The Doctor wanders off alone with his instrument, following a narrow path worn through the scrub. The TARDIS has landed near the top of a hill and the path downward is a well-travelled one. He seems well pleased as he stops and takes a reading on the hand-held instrument. Laughing to himself, he moves on. He is unaware that the primitive man, dressed in animal skins and carrying a club, is following him at a distance.

Back at the TARDIS, Steven and Dodo wait outside. Steven is already worried about the Doctor's extended absence, but Dodo thinks it merely typical that the Doctor has lost track of time. She refuses to get riled up, instead choosing to needle Steven for letting the Doctor go off alone in the first place if he was going to get so worried. Steven decides to ignore her jibes and move off a bit to see if he can catch sight of the Doctor.

But the Doctor's path downhill has taken him out of sight. Besides, he is too absorbed in his readings to care much about the passage of time. The latest readings seem to confirm the Doctor's assessment of their location. He thinks his companions will be pleasantly surprised.

From behind the bushes, the primitive man watches. He is soon joined silently by another.

Steven has begun calling out to the Doctor. He hears the calls and is annoyed by their insistence. He calls back, but only half-heartedly. Steven cannot hear him. Soon the Doctor has more to worry about as he detects movement in the bushes near him.

Hearing no response to his calls, Steven decides to go further down the hill in search of the Doctor. He calls back to Dodo before he does so and she sits down on a rock near the TARDIS to wait. Before long, she hears the sound of loose stones trickling down behind her. Dodo gasps and turns, but there is no one there. She looks around cautiously for a moment, then, certain her imagination is playing tricks on her, she sits back down, facing away from the hillside.

But there is someone there. Another primitive peers over the top of the hill. Seeing Dodo looking away again, he begins to clamber down toward her, axe in hand. But he again makes noises which alert her to his presence. She turns and screams at the sight of him. The sound drives the primitive off and brings Steven running. Dodo tells him all about the "savage" that she saw. Thankfully he is gone now. Steven is sceptical, remembering the Doctor's description of this place as a future time of peace and prosperity, but Dodo is adamant about what she saw. Steven is convinced, certain they have actually arrived at the dawn of man.

Seeing nothing in the bush, the Doctor decides to start back up the hill toward the TARDIS. His final reading has shown that they are in the prosperous future era that he thought and he can't wait to show his companions.

Behind the screen of bushes, the two primitives watch him. He is now coming directly toward them. The two speak fairly clearly, not like brute savages. Indeed, the younger of the two actually seems afraid of the Doctor, not hostile towards him. This newcomer is clearly not like them, but he is unarmed, unlike "the Elders" that they also seem to fear and hate. The younger man thinks they should run from the man, but the other wishes to kill him.

The Doctor's life is saved when two more men approach from behind. These are not savages, but futuristic soldiers, wearing synthetic uniforms and boots. Both are armed with energy weapons. The Doctor turns, startled. He forgets about the sounds in the bushes, assuming these two men were responsible for the noises he heard. Despite their weapons and uniforms, the two men - Exorse and Captain Edal - are quite pleasant. Both warmly greet the Doctor and welcome him to their planet.

The Doctor learns that the Elders of their city have been observing his time-space travels for some time. They know him as "The Traveller from Beyond Time" and they had predicted that he would soon be arriving here. Edal and Exorse were sent to greet him. The Doctor seems to take all of this in his stride, still not sure what to make of it.

Captain Edal seems concerned when he spots the instrument the Doctor carries. He mistakes it for a weapon, which the Elders believed he did not carry. The Doctor explains it is a Reacting Vibrator, helpful for making his calculations. The Doctor mentions his companions and again gets an odd response from the two men. They have no information about any companions and no instructions from the Elders on what to do with them. The Doctor wishes to go back and fetch them, but Edal will not let him go. At first, the Doctor is offended by the officious tone of command, but Exorse smoothes it over, saying the Elders are most anxious to welcome the Doctor themselves. This seems to mollify him and the Doctor agrees to go with Edal, as long as Exorse goes to fetch Steven and Dodo. He does so, following the path as the Doctor indicates. Edal leads the Doctor further down the hill.

Steven has turned his attention back to the absent Doctor. He's certain there's something wrong and is determined to go after him. Dodo doesn't want to be left behind again and starts downward with him. However, she is attuned now to the sounds from behind her and she stops and turns when she hears them again. This time Steven tells her she's imagining things, determined to keep going. But he's stopped when a stone-tipped spear thuds into the ground in front of him. It's razor sharp - primitive but deadly. Steven is now convinced of what Dodo saw and decides retreat is the best option. They hurry back up the hill toward the TARDIS.

Suddenly spears begin raining down on them and they must dodge to avoid them. But just as suddenly the attack stops, at the sound of a shout that echoes commandingly all around. It also stops Steven and Dodo. They scan the area for the source.

It is Exorse, who appears from below, beaming at them as if nothing was wrong. He welcomes them both by name, telling them that "the Traveller" sent him. Once they find out that the Doctor is all right, Steven relaxes. But Dodo is still concerned about the savages. Exorse avoids talking about them, saying instead that "some of us are fairly civilised". Clearly the Doctor was right and this is the future, despite how it first appears. Exorse urges them to come with him to the city to be welcomed by the Elders.

Meanwhile, the Doctor has been brought into the main council chamber in the city. It is large and ornate, indicative of the prosperity of the community. There is a crowd milling around, servants and citizens alike. In the centre of the room sits a large raised bench at which sit four men in elaborate robes. These are the Council of Elders. Led by Jano, they welcome the Doctor effusively. Jano points out a large star map which charts the Doctor's voyages through time and space. They have followed his travels for a long time and feel that it is a great honour to them that he has arrived here.

To repay that honour, Jano offers the Doctor the office of one of the city's high elders. He is fitted with a robe like the others. Jano calls the Doctor "the greatest specialist in time-space exploration", far above their own researches. The Doctor accepts the robe without question, but not the complement. He has seen in just his brief time here much evidence of advanced scientific achievement, corresponding to all the stories he had heard of a highly intelligent and civilised race here in this part of the universe. He thanks them for making him appear so grand.

Shortly Dodo and Steven are brought in by Exorse and Jano welcomes them. The Doctor shows off his cloak. Dodo is impressed, but Steven is still sceptical. The Doctor tells him that he was right about this being an age of peace and prosperity. Jano begs forgiveness of Steven and Dodo for not anticipating their arrival with the Doctor. While he cannot give them the same honour bestowed on the Doctor, he can offer them gifts from the community. Steven is given an ornate dagger and Dodo is given a hand mirror inlaid with diamonds and other precious gems. Both seem pleased.

Jano also offers the two young people the chance to look around the city, providing two young guides to show them around. The Doctor thinks this a fine idea, shooing them off and chastising Steven for not believing him about where they had arrived. As his companions are led off, the Doctor sits down and prepares to answer the councillors' many questions.

Outside the city, Exorse and Captain Edal are back on patrol. They are no longer the cheerful fellows who greeted the Doctor earlier. Edal is particularly agitated, grumbling about the tremendous welcome accorded this Doctor. He never trusted strangers and certainly would never allow this old man to be treated as one of them. But he is just a soldier and there is nothing he can do, so he drops the subject.

He and Exorse split up to patrol different areas. They are watched by the two male primitives who observed the Doctor earlier. They are called Chal and Tor. This time they are joined by a woman called Nanina. Chal is clearly in charge of the group. He knows that the soldiers are out "hunting" and sends Nanina back to their caves to tell their people to hide. He warns her to go carefully while he and Tor go to warn others of their group elsewhere.

Avon and Flower show Dodo and Steven around their city, speaking of it in wondrous, glowing terms. On the subject of environment, they explain that the city is a self-sustaining indoor ecosystem, its sun, wind, and rain all artificially controlled by the Elders. Avon and Flower seem awed by the accomplishment, but Flower expresses a little regret that she's never experienced real wind, rain, or sunshine. Avon goes on to say that every citizen has the opportunity to pursue whatever career path best suits them and everyone can become the best they can be.

Steven is naturally intrigued by this, noting that most other civilisations have failed to make this utopian advance. He wonders how this community has managed it. Avon beats Flower to an answer, saying that with one simple discovery their scientists have given the people greater energy, intellect, and talent. Of course, he refuses to identify the discovery, saying that it is a subject best left to the Elders and the Doctor.

Indeed the Doctor has come to that very same question with Jano and the other Elders. He tells them that he cannot accept their accolades and gifts without endorsing their lifestyle. To do that, he must know more about them. He knows they are far more advanced than most civilisations, but he does not know how it was achieved. Now he would like to know.

Outside, Nanina has not gotten far into the area known as the craters before she catches sight of Exorse not far away. He is hunting her. She dives for cover behind some bushes, hoping she is well enough hidden.

From their new vantage point above, Chal and Tor can look down on the craters and see what is happening. They watch as Exorse moves inexorably toward Nanina's hiding place, helpless to assist her. All they can do is call to her to run. She does so, but is unaware of Exorse's exact location. She actually runs closer to him and right into his line of fire. Exorse draws his gun and fires. Nanina is engulfed in intense light and she freezes, unable to control her own limbs. By moving his gun, Exorse can now control the girl's movements. They leave the craters, heading toward the city. The "hunter" has captured his prey. Chal and Tor watch helplessly.

In the Council chamber, Jano answers the Doctor's question. Life preys on other forms of life, he says grandly. Mankind "preys" on food, water, oxygen, etc. But the Doctor knows that this simplistic explanation does not describe what this society has done; they have found a much more effective source of energy. Jano calls it the "energy of life". Their scientists have found a way to "tap it at its source" and recharge themselves with life's vital force.

Chal and Tor have come down the hillside in pursuit of Exorse. Catching up to him, they jump into his path, Chal offering himself in place of Nanina to save her. But Exorse carries on past them without a word, ignoring them as if they weren't even there. Meekly, the two men give up.

Jano shows the Doctor a model of the machinery which taps, stores, and distributes this "energy of life". The Doctor is little interested in the mechanics of the process, wanting to know instead what is the source of the energy. He is sure it must be a very high form of life they are tapping. Jano tells him they absorb only "a very special form of animal vitality".

Unchallenged now, Exorse brings his captive nearer the city walls.

Flower is now leading the tour, which is beginning to get a bit tedious. Even when she tells Steven and Dodo about their games and dances it's deadly dull. Dodo starts to lag behind, noticing a small passageway ending in a window which Flower didn't comment on as they passed. Avon sees her as she starts to go down the passage and stops her. That passage leads to the outside world, where the citizens are not allowed to go.

Flower tries to put the best face on the situation, explaining that they have everything they need in the city and so have no need to go outside. But this does not sit well with Steven and Dodo. They ask about the men who came to find them and Flower says they are guards. Dodo assumes they are meant to keep back the savages. Avon tries at first to pretend he doesn't know what she is talking about, but then admits they exist and that the guards' job is to keep them away. The savages are why the citizens seldom go outside the city.

As the tour continues on toward the stadium, Dodo stays behind. She gets down the passage and looks out the window just as Exorse walks by, pushing Nanina ahead of him with the power of his light gun. She is horrified by what she sees. She races back and catches up with the group just as they start to miss her.

Avon and Flower stop to confer with each other, trying to decide which way to go next. Dodo draws Steven aside, explaining in a whisper what she saw outside. Unfortunately, Steven appears to have bought into the utopian vision presented here. He thinks it unlikely that the guards would need to take prisoners in "a place like this", even if it was a savage. Her description of the light gun also stretches his credulity. She presses the issue, wondering why Avon and Flower are so cautious and selective in what they show them, but Steven tells her she's imagining things.

Flower notices them whispering and is suspicious, but Steven hurries to join her and Avon, dragging a cranky Dodo with him. The endless tour resumes.

Exorse finally reaches a doorway into the city. As he moves toward the door, he deactivates his light gun. Nanina slumps against the wall, reeling from the effects of the paralysing ray. She begs him to let her go, knowing full well what awaits her inside. Exorse ignores her as he ignored the others, and activates a control beside the door.

In the main laboratory complex, a group of scientists work at a series of advanced machinery in two rooms. Two men wheel a gurney from one room to the other. On it is a male savage. He looks weak and worn and is extremely disorientated. He moans quietly and his gaze wanders. A bell rings and the chief scientist, a man called Senta, looks up from his work testily. He knows it is Exorse, behind in his deadline.

Before he answers the bell, Senta stops to examine the savage on the gurney. Senta seems concerned that the man is very "depleted"; his vitality reading is a very low 17.4. Senta blames his technicians for not following instructions during the energy transfer, but believes that the savage will recover. He has before.

The secret of this society is now very clear - their energy comes from tapping into the very life essence of the savages. The strong prey upon the weak.

The bell rings a second time and again Senta reacts angrily. He cannot believe that Exorse can keep him waiting for so long and then expect an instant response as soon as he rings. The chief scientist takes his time finishing his examination of the savage. When he is finished, he instructs an assistant to take the man away and release him. He is to go to the emergency exit in corridor K-O-4 to do so.

As soon as they leave, Senta activates a control and a door opens. Exorse enters, pushing Nanina ahead of him. Senta gives her over to two scientists to prepare her for an energy transfer, then lights into Exorse for being late and putting him behind schedule. The guard tells him he was delayed by the arrival of the strangers, whom he had to go and fetch. Senta is very curious about the strangers, wondering what they are like. Clearly he has heard much already. Exorse says that while they look normal, there is something different about them that he cannot quite describe. With that, Exorse is ready to leave. Senta returns to work, very aware of his deadline. He authorises the transfer of Nanina's life energy, instructing the technicians to make certain not to go below vitality reading 24 this time.

Steven has listened intently to Avon and Flower during their tour and is duly impressed with their city. But he is not without questions. He wonders why all of this innovation is confined her inside and not extended into the countryside. Avon's response is quick and sharp: they have everything here that they need.

In the laboratory, Senta completes the final checks on Nanina, who is now strapped to a gurney. She is begging Senta to stop this and leave her alone. Her fear grows and her pleas get more insistent as she is wheeled into the inner laboratory.

Dodo, no longer listening to a word being said by their guides, lets her gaze wander. She spots a movement and sees Exorse coming out of a doorway and disappearing into the streets. Remembering him as the guard holding the savage woman prisoner, she slips away from the others and goes through the door before it closes.

In the Council chamber, Jano continues to extol the virtues of their revolutionary energy transfer. With their knowledge, they can increase bravery, wisdom, strength and beauty. They can reach perfection. But in this rhetoric he still does not reveal to the Doctor the source of this tremendous energy.

Avon, Flower, and Steven are some way along before they realise Dodo is no longer with them. Steven is angry at her disobedience and joins Flower in calling after her.

But Dodo is in an eerily silent metallic corridor. She has taken several turnings and has no idea where she is. There are no markings, no windows, and no doors. As she continues on, she begins to hear the sounds of ragged breathing and shuffling footsteps, at first quietly and then growing in volume. Someone is approaching her. With the echoes in the corridor she cannot pinpoint the direction of the noises and so moves forward to a junction. The noises are getting louder and her bravery is starting to desert her.

Dodo hesitates as she reaches the junction but then screws up her courage to look around it. Right in front of her is a male savage, wild-eyed and crazed. His breathing is harsh and his mouth is slack. His arms are outstretched and he lurches crazily toward her.

But Dodo is really in no danger. The savage approaching her has been so depleted by the energy drain that he is moving by instinct alone. He appears totally unaware of Dodo's presence in the corridor and staggers blindly past her and toward an outside door at the far end of the corridor. Slowly and painfully he makes his way toward the door, looking very weak and in danger of stumbling over at any moment.

Dodo watches in total silence as he goes, rooted to her spot. At last the man nears the door and trips some invisible mechanism. The door slides open, light flooding into the dim metal corridor. However, the man's ebbing strength gives out, so near to his goal. He stumbles and collapses, partially outside the door. He groans in pain, trying to get back up. Dodo's natural concern for others asserts itself and overrides her memory of the earlier savage spear attack. She runs to help him.

Finally aware of her presence, the savage looks up into her face. The look of anguish in his eyes touches Dodo deeply. She summons up her strength and drags the man outside. As if they had been waiting for just this moment, Chal and Tor approach Dodo from their hiding place nearby. They shove the girl away and take charge of their comrade, helping him to his feet. The hotheaded Tor, seething with anger over the treatment of his people, makes a move to strike Dodo. But the man whom she saved, known as Wylda, puts up a feeble hand to stay Tor. He cannot speak but shakes his head and Tor reluctantly backs off.

There is much that Dodo wishes to say, to ask. But the door behind her suddenly begins to glide closed. She reacts instinctively and hurries back inside without a word. She does not fully understands what she has witnessed, but she knows it does not jibe with the peace, prosperity, and civility the Doctor has praised in this community.

In Senta's laboratory, Nanina's energy transfer begins. She has been confined in a glass case in the inner laboratory, still begging weakly to be let go. As the process begins, a mist fills the case. It draws the life energy from the girl slowly and transfers it to a series of clear jars in the outer lab, which fill up with a bubbling misty liquid.

Inside the city, Steven, Avon, and Flower continue their search for Dodo. They have had no luck. Avon in his simple way suggests she might be playing a game with them, but Steven knows that is not like Dodo. He fears that something may have happened to her.

In the lab, the transfer continues. The sounds of machinery grow rather loud, drifting out into corridor K-O-4.

In the council chamber, Jano continues to extol the virtues of his society's new "stimulant" as the Doctor listens, an unreadable expression on his face. But Jano's monologue is interrupted when Steven bursts into the chamber to tell the Doctor of Dodo's disappearance. He is out of breath and speaks quickly and urgently. Jano finds this excess distasteful and turns to Avon and Flower to explain. It is the same message but delivered with reserve...and a touch of fear. But neither the Doctor nor Jano will admit to concern. The city is a place where no harm can come to you, they say. Besides, she cannot leave the city and she is fully capable of looking after herself. The Doctor tries to get the agitated Steven to leave so that he and Jano can finish their discussion.

As Nanina's transfer nears its critical stage, Dodo finds her way into the laboratory, drawn by the sounds of activity and voices. No one notices her at first as they busy themselves slowing the rate of energy extraction. But soon an assistant sees her as she moves forward to get a better look at Nanina slumped weakly in her cubicle in the inner part of the lab.

The man leaves his post and sneaks up behind Dodo, attempting to grab her. However, she notices the movement and turns on him. Her shouts attract the other assistant on duty in the outer lab, who joins in the effort to subdue her. Together they get hold of the struggling girl and try to figure out who she is and why she's here. They have no record of her impending arrival but assume that if she is here she's intended for transference. Dodo isn't sure what that means, but she has seen enough to know it's not good. Her voice is full of dread as she cries out to try and stop them.

The search for Dodo has resumed, with Captain Edal now in the lead. The lack of concrete information from Steven, Avon, and Flower however is making him quite cross. They are retracing their steps in the last place they recall seeing Dodo. They pass by the window she looked out of, but it is far too small for her to have crawled through. Frustrated, Edal promises that Avon and Flower will be held responsible for their negligence. Steven listens to this, wondering why everyone is so worked up over a lost girl, but his only concern is finding Dodo.

The group continues on, passing by the barely-visible doorway set into the wall. However, Edal stops before it. He has a bad feeling. Avon and Flower are certain she couldn't have gone down there and their voices carry a tone of dread. Edal operates a hidden control and the door opens. He is very serious now and Steven is worried. Edal says only the guards use this entrance and that if Dodo went inside, he wouldn't give much for her chances. Steven is alarmed by these words.

Edal turns on Avon and Flower, his voice threatening. He is certain this is where Dodo has gone and these two children will pay for letting her out of their sight. Flower is nearly in tears. She knows that the area beyond the door is forbidden; Dodo wouldn't dare go inside. She says it with more hope than conviction. Steven is quick to point out that Dodo would be first in the queue to go into a forbidden area if she was curious and he tries to dash through the open door in search of her. But Edal quickly bars his way and barks an order for him to stay put.

In the interior laboratory, Senta monitors the final stages of Nanina's extraction. He is interrupted when one of his assistants enters and tells him of the trouble they're having with a new arrival. Senta leaves one assistant on duty inside and returns to the outer control area to find the third assistant trying to catch Dodo again. She has struggled free of him and now stands behind the trolley. She is very vocal in her opposition to becoming a part of whatever is going on here and uses the trolley to continually dodge the scientist.

Senta watches in horrified fascination, unsure what to do. The assistant stalking Dodo tries to dodge round the trolley again and this time succeeds. Dodo dodges away and finds herself up against a bank of instruments with nowhere else to go. Suddenly she grabs a heavy metal apparatus from a bench nearby and raises it over her head. She orders the men to keep back or she'll smash the entire bank of equipment. Her tone is resolute and unmistakable. Senta, bewildered by this response from an extraction subject, nevertheless orders his men to stand back. She could kill them all if she smashed the vital equipment.

Steven tries to force his way past Edal, but the guard captain grabs him back. Steven is certain Dodo is there, and Edal is forced to agree. But only he can go inside. He does so, closing the door behind him and leaving an angry Steven outside with Avon and Flower.

In the inner laboratory, the lone assistant is hard pressed to keep an eye on all the machinery. He had expected Senta back long before now. He turns to see the energy collection jars bubbling furiously and becomes alarmed. He tries to stem the tide of the extraction and fails.

In the control area, Senta learns to his horror that Dodo is not from the outside but is one of the "travellers from beyond time". He cannot believe what was nearly done to her and wonders aloud how she came to be in here.

However, his questions are interrupted by a worried shout from the inner laboratory. Senta realises that he has completely forgotten about the extraction in progress and rushes back inside. He orders his assistants to break all connections immediately. Shortly the bubbling in the jars and the sounds of machinery die. But a worried Senta continues to rush around, checking readings.

Dodo, forgotten in the chaos, has put down her "weapon" and entered the inner lab. She stands watching all of this, seeing that the object of this experiment is the young female savage she saw through the window. So absorbed has she been in trying to understand it all that she has not seen Captain Edal enter. He is furious when he confronts her, but Dodo shows no fear. Senta rounds on the guard captain, threatening to report the girl's intrusion and inferring that it is his fault she's here. When Senta learns that the Elders are already aware of what has happened, he gives up his outrage and simply wants Dodo removed so that he can get back to work.

Dodo leaves the inner lab with Edal, actually glad to be away from the gruesome scene, but she is full of questions and demands answers of Edal. What is all this for? Edal will not answer and simply drags her off. Seeing that he is still armed with the weapon she saw earlier, Dodo goes along with him.

Back in the lab, Senta and his assistants remove Nanina's body from the cubicle. She looks tired and drawn and is completely unconscious. The assistants gather round to see if she is even still alive. Senta examines her quickly and is relieved to find that she is. But they have been lucky, he says. She has had far too much energy extracted and she was nearly killed. It must be quite some time before any more life energy is taken from her.

Dodo, led by Edal, is returned to Steven, Avon, and Flower. She reacts angrily when Steven grills her about what happened. She says she was attacked by "some sort of mad doctor" and demand to know what that place is. She wonders if it is a hospital and Avon is quick - too quick - to agree. It is clear the citizens here know their own dirty little secret and they are all trying to cover it from their "honoured guests". If that was a hospital, Dodo doesn't like the way they treat their patients. Edal is concerned by this comment and demands to know what she saw there. But Dodo wisely admits to nothing, calling the laboratory sterile and inhuman instead. Steven says she is imagining things and this seems to break the tension.

Edal leads Steven and Dodo off to stand before the Elders, warning Avon and Flower to stay put. They, too, will be taken before the Elders in due time. Dodo is concerned that her actions may get the young people in trouble, but Avon assures her they'll be all right. Perhaps they'll even see each other again. However, once Dodo and the others are out of earshot, Avon's cheerfulness disappears. He must work hard to convince a fearful Flower that their society is fair and just and will not harm them for an innocent mistake.

For her part, Dodo is simply glad to be out of Senta's laboratory. Steven's concern for her well-being indicates that he believes her story. Dodo promises not to wander off again, but it has nothing to do with Steven's concern!

Back in the lab, Nanina has been freed from her restraints as she has regained consciousness. As with Wylda, the previous extraction subject, Nanina awakes glassy-eyed and dazed. She barely realises that Senta is speaking to her. He tries to get her to understand that she is to go. But it is more out of instinct than obedience that she finally gets up and tries to move away from him. The girl is far too weak however, and she collapses almost immediately. Senta orders his assistants to help her to release bay 4 and then busies himself at other tasks.

In the council chamber, the Doctor is still amiably talking with Jano and the other Elders. They are interrupted by the arrival of Edal with Dodo and Steven. The Doctor is glad to see Dodo, but chides Steven again for being overly concerned at her absence. Dodo is anxious to tell the Doctor all that she has seen, but he says he doesn't have time. He wishes to go to the TARDIS to fetch some documents that may relate to some of the Elders' scientific questions.

Jano is suspicious of this wish to leave, but the Doctor's mood is genial and pleasant. He promises to return shortly. Edal offers to send a guard as an escort, but the Doctor politely refuses. Steven will go along to help him and Dodo will join them so they won't "lose her again". With that they are off.

Waiting until they are gone, Jano addresses Edal, wanting to know if Dodo learned anything of consequence. Edal is convinced she understood nothing of what she saw, but she may suspect something. Jano knows it is impossible to know what the Doctor is thinking and so believes it would be wise to keep on eye on them all. Edal hurries to follow the strangers.

Out in the wasteland, the Doctor leads his companions back up the hillside toward the TARDIS. Dodo is bursting to tell her story, but the Doctor has waited until now to hear it so that they would be alone. He admits that he does not entirely trust Jano and the Elders. He has no concrete proof but suspects that things are not right here. Steven and Dodo are surprised at the Doctor's apparent change in attitude.

However, before they can discuss the matter further, Steven spots a figure lying on the ground partially hidden in the scrub. It is one of the savages. As they get nearer, Dodo recognises it as Wylda, the man she helped earlier. He tries to get up when he hears the strangers approaching, but he is far too weak to move. Dodo wonders where the other two are as there is no sign of them. She goes to the man's side, Steven and the Doctor right behind her.

The Doctor examines him and asks Dodo some questions. He learns that Wylda left the laboratory in this depleted state and everything becomes clear to him now. His fears have been confirmed the great advances of this civilisation are based upon the transfer of life energy from the savage into the citizens. They are revitalised and the savages are left like this, depleted of energy and nearly dead.

The Doctor hands Steven the key to the TARDIS and sends him to fetch some capsules marked D4O3. He thinks they will help revitalise Wylda and save his life. He also passes along the reacting vibrator instrument to be returned as he doesn't need it any more. Steven goes off quickly, Dodo right behind him. The Doctor stays behind to care for Wylda. He speaks encouragingly and instructs him to breathe slowly and deeply.

Suddenly Captain Edal appears behind the Doctor, offering "assistance". The Doctor, so outraged by the treatment of these people, abandons any pretense of pleasantry, directly blaming him for Wylda's condition. Edal is unfazed, saying that the savage is probably just lying there because he's "a lazy animal". He prods the savage with the toe of his boot, trying to get him up and moving.

The Doctor is appalled at this conduct and demands that Edal desist before he kills Wylda. But Edal prods him again, harder this time, saying the Doctor doesn't understand. But the Doctor does understand - only too well. These "savages" are human beings just like Edal and the Elders and they are being treated worse than animals. He points out that Edal is currently behaving in rather a sub-human fashion himself. Edal is angered by these words, insisting that the savages are far less developed than his people. The ugliness of this society comes out in full in his words. He moves forward to kick Wylda again and this time the Doctor stands in his way. Edal's anger boils over and he orders the Doctor to return to the city with him at once, but the Doctor has no intention of doing anything of the kind. He will stay and look after Wylda and that is final. Edal draws his light gun and points it at the Doctor. He will come along or face the consequences.

Shortly, Steven and Dodo return from the TARDIS with pills in hand. However, they are very concerned when only Wylda is there and not the Doctor. Steven calls out for him but receives no response. He thinks the Doctor may just have wandered off and scans the surrounding area while Dodo gives one of the pills to Wylda. Weakly, he takes it.

Elsewhere in the scrubland, Chal and Tor lead a group of savages down the hillside. They are all armed with spears and clubs.

Dodo, encouraged by Wylda's rapid improvement, gives him a second pill. Hopefully it will work equally well. As Dodo stands up again, her gaze travels up the hill. She spots the group of savages descending and notes their weapons with great concern.

The hotheaded Tor spots Steven and Dodo standing over Wylda and his anger surges. He is ready to kill them both in revenge for Wylda and for all of their people harmed by the Elders. Chal realises that there will be a terrible price to pay if they harm any of the city's residents, even these strangely-dressed ones. Tor thinks it is the only way to save Wylda, but Chal knows differently. They will not let Wylda die, or that will be one less source for their vital life energy.

Dodo and Steven look for options. They could go back to the city, but Dodo is too afraid after her experiences. She suggests the TARDIS, but Steven thinks that a bad idea as they would be easy prey on that path. They should stay here, he says, and talk to the savages. They need to learn whether the savages have taken the Doctor. As the group approaches, Steven warns Dodo to try and hide her fear. Chal and Tor arrive to face them.

Tor is unable to contain his anger once he is face to face with what he thinks are unarmed citizens and he threatens to kill both Steven and Dodo. He raises his spear to attack but is stayed by Wylda, who speaks for the first time. He tells his people that Dodo and Steven are friends and should not be harmed.

Chal notices the pill container that Steven holds and interrogates him. When Steven says he thinks Wylda is "sick", Chal begins to believe that he and Dodo are not from the city after all. Tor is less convinced, nothing that they saw Dodo there. This gives Chal pause, but Wylda speaks again, his voice strengthening. He tells his people that Dodo helped him when he needed it and that their friend, the old man, spoke against the treatment of the savages. He also reports sadly that the Doctor has been taken prisoner by Captain Edal, who turned against their "guest" when he tried to protect Wylda. Steven and Dodo seem to forget their own plight and are now more worried about the Doctor.

Jano takes an arrogant tack when the Doctor is brought before him, seething with indignation. He asks the Doctor how he can condemn their great civilisation because of a few "wretched barbarians". But the Doctor's outrage is clear and direct. This society's "progress" is worthless if it cost "even one soul" to achieve. Their "advances" are meaningless to him.

Jano refuses to argue, sounding almost sad when he orders Edal to take the Doctor away...to Senta's laboratory. He does not know what this means, but resists nonetheless as Edal tries to grab him. He cannot break free when Edal activates his light gun.

Outside, Steven urges Chal and Tor to help him rescue the Doctor, but they are certain his fate will be the same as theirs - he will be used an energy source. And there is nothing they can do to stop it.

Once in the laboratory, the Doctor is freed from the light ray. Senta, not realising at first what is happening, greets the Doctor warmly. His curiosity about "the traveller beyond time" is undimmed. But Edal cuts through the pleasantries and orders Senta to cease all other work and prepare for an emergency energy transference. Still not realising, Senta thinks the Doctor is here as an observer. The Doctor too is under this impression and refuses the "honour". Edal must then spell out that the Doctor is to be the subject whose energy is extracted.

Senta is aghast, nothing that he's never attempted a transference with so high a life form. His protest sounds like refusal. Jano enters at this moment and cuts through Senta's protest and orders him to comply. Meekly, Senta agrees. This time it's the Doctor's turn to protest and he does so vehemently. However, as he tries to leave the lab, Edal again draws his gun and traps the Doctor in the paralysing ray. He is helpless to resist. Pleased, Jano leaves as the Doctor is strapped to a trolley.

Senta, knowing that his leader is not to be questioned, goes to work quickly. As his assistants ready the transfer equipment, he makes a note to open a special computer file on this transfer. They must monitor and record everything that happens in this unique experiment.

It does not take long before the Doctor is in place in the glass cubicle and surrounded by gas, just as Nanina was. Almost immediately, the jars begin receiving his vital energy. The levels rise quickly and the assistants are concerned. But Senta is certain the Doctor can take it. He even ups the extraction rate a couple of points. The collection jars bubble furiously as they fill.

The Doctor's energy transference continues and Senta has managed to overcome his awe of this historic experiment and focused his attention back on the machinery. He is very concerned about the Doctor's vitality level and imposes a cutout at 25 to make sure he is not taken too low.

Jano returns to the laboratory with Captain Edal, having received a message from Senta. He arrives at the end of the process and he congratulates his chief scientist on the success of the transfer. He is relieved to hear that the Doctor is in good condition. Given time, he will recover and will be able to be used again. Jano is anxious to see this happen, sure that the high-quality energy will be very valuable to their people. He also decides to do the same with Steven and Dodo. He believes they are as big a threat to this society as the Doctor was. By harnessing their high-quality energy, he can achieve multiple goals. He instructs Edal to send out patrols to find Steven and Dodo.

Chal, Tor, and the others have taken Steven and Dodo to their home - a flat plain in front of a high rock wall with cave entrances set into it. It is featureless and bare, but they should be safe. Another group of savages mill about, several tending to a man who is recovering from the energy extraction process. Steven goes to help the man, but Chal tells him to leave it. Steven is angry that they have refused to try and help the Doctor, but Chal is certain they cannot help him against the guards' light guns. Steven is alarmed to hear that they have retreated here only to hide, as these people have always done. He wants action.

Tor has gathered some news from their people and passes it to Chal guard patrols have been sent out from the city, and they are not hunting for savages. With no news of the Doctor, Dodo is truly worried to hear this. Steven tries to assure her that they will escape and find the Doctor. Chal overhears this and tries to warn them again - as gently as he can - that if the Doctor has been subjected to energy extraction, he will not be as they remember if they find him again. The process leaves all of its victims hollow shells of themselves.

Senta tells Jano that the Doctor's vitality level is at a safe 25. He was careful not to take it too low. But that said, the energy extracted was very high indeed. He will recover, and will be used again.

Jano then surprises Senta by ordering him to prepare for an immediate in-transference of energy - the Doctor's energy. Even more surprising is that there is to be only one recipient of this energy - Jano himself. He justifies this by saying that such a transference of high-level energy could be dangerous and it would not be wise to risk other citizens' lives. However, the true reason - the prospect of acquiring the energy of such a highly-intelligent life form - shows plainly on his face.

Senta tries to warn Jano of the danger of such an unusual in-transference, but Jano cuts off all protest. He orders Senta to inform him when all is in readiness and storms out.

Outside the city, the guards continue their all-out search for Steven and Dodo. So far there has been no success, but Captain Edal orders Exorse to take his men to the Valley of the Caves. Exorse looks a bit worried as the dwelling place of the savages has usually been off-limits. But Edal's orders are clear and the search narrows.

The news of an approaching patrol reaches Chal very quickly. Steven and Dodo become worried anew, looking for some safe place to hide, but an angry Tor tells them there is no safe place. The guards have never come here before, and now they are coming for the strangers, putting the lives of the entire group in danger. He is livid when Chal offers to hide the strangers in their caves, but Chal asserts his authority and orders it. He respects the trust that they have put in him and he wishes to honour it now. Tor angrily puts the destruction of their people on Chal's head.

Dismissing Tor's fears, Chal leads Steven and Dodo into the cave. Inside, Nanina and Wylda are recovering from their energy extraction. Nanina shudders at the sight of the strangers, but Wylda calms her. Dodo marvels at the inside of the main cave area. It is not as she had expected - squalid and dank. Instead it is large, airy and welcoming with elaborate murals adorning the walls. She likens it to a temple. Chal responds proudly, telling her it was created by their ancestors, a spiritual race of great artists. As time has gone on, all of their skills have been taken from them through the extraction process. All his people have left is their faith, and that the Elders will never take from them.

Steven and Dodo are impressed by this, all their preconceived ideas about these so-called savages wiped away. However, their immediate problem comes back to the fore with a shout from Tor outside. The patrol is already here.

Exorse appears, light-gun drawn, before Tor and the others, keeping a distance borne of loathing and not a little fear. The rest of the patrol stays well back for the same reasons. When Tor will not tell him where the strangers are, Exorse activates his light gun. Tor is caught in the beam, helpless. Generations of fear and years of personal experience come to him and when Exorse asks again, Tor cannot help but indicate the caves. Ignoring the rest of the savages, Exorse heads to the cave mouth and calls inside.

Chal has lead Steven and Dodo further back into the main cave, out of sight. Nanina, unable to move quickly, has stayed. She denies that Steven and Dodo are inside. Steven, keen to do something other than simply hiding, moves out of the darkness and speaks quietly to Nanina. He is glad to learn there is only 1 guard, but the light gun leads him to reassess a direct confrontation. As Exorse peers into the cave, still somewhat afraid to enter, Steven returns to Chal and Dodo. Steven learns to his horror that there is not other exit from the caves, but Chal hopes to lose the guard in the maze of passages if he comes inside at all. It is their only choice at the moment.

Exorse still hesitates at the cave entrance. He tries to order the savages to produce Steven and Dodo. When there is no response, Exorse screws up his courage and goes inside.

Steven and Dodo can hear the booted footsteps inside the cave now, but are quite some way down one of the many passages. Dodo is worried that they are bringing more suffering upon Chal's people, but he assures them that being hunted down is an all-too common occurrence. Chal hurries them deeper down the passage.

Exorse enters the main chamber, holding his light gun before him. He finds Nanina and Wylda and notes the numerous passages off the main chamber. Nanina refuses to tell the guard where his quarry went and Wylda says nothing at all. However, a third savage cowering near the back of the chamber is not as strong. Despite Nanina's entreaty, the man sees Exorse light gun and gives away the passage Chal and the others took. As Exorse goes, Nanina bitterly condemns the terrified man.

Further down the passage, Chal continues to lead Steven and Dodo. He reminds them that there is no escape from this passage and their only hope is that the guard goes a different way. However, Dodo detects the sounds of pursuit and this hope is dashed. They continue moving, trying to be as quiet as possible. But Exorse hears their echoing footsteps and knows he is on the right track. Chal offers the hope that the guard won't continue, but it is a vain one. There is very little left to the passage they are following and then they will be trapped.

Exorse calls out, taunting his quarry. His voice echoes all round, amplified by the rocks. Dodo is ready to give up, but when Steven sees the find bend up ahead, he has a plan.

Tor, recovered from the effects of the light gun, joins Wylda and Nanina inside the cave. He learns what has happened, Nanina still angry at the savage who betrayed the strangers. Tor, knowing what he did, is torn. He wishes to support the strangers who have helped his people, but his fear of the guards is too strong. He knows what they can do.

Steven, Dodo, and Chal turn the final corner and Steven begins to taunt Exorse right back, hoping that he'll get angry and make a mistake. Chal is afraid, especially of the guard's light gun. Steven learns about the paralysing light beam and gets an idea. If the beam can be reflected, they might yet get out of this. Chal confirms he has seen one of the beams reflect off of a clam lake surface before. Emboldened, Steven takes a mirror from Dodo and urges her to get down on the ground.

Exorse continues to taunt Steven, but he gives it right back as he gets into position near the turning in the tunnel. The taunts work and Exorse activates his gun, sweeping the light beam down the tunnel wall as he advances incautiously. Chal can't resist looking up, but Steven yells at him to get back. Chal's fear starts to get the better of him and Dodo must forcibly hold him to keep him from submitting himself to the advancing light.

But soon Steven's plan has worked. The light beam is reflected off the mirror and back into Exorse's face. The guard freezes and drops his gun. The beam cuts off but it takes precious seconds for Exorse to recover. Before that time, the light gun is in Steven's hand and activated. He heads the guard back down the passage, Chal following. Generations of oppression for his people have been reversed with this one action and he is duly awed. Dodo joins them.

Tor huddles in the main area of the cave with the others. He hears footsteps returning down the passage and assumes the worst. The inbred fear in his people comes to the fore and he cowers as Exorse emerges. It becomes quickly apparent what is happening and the savages leap to their feet in amazement. Steven releases Exorse from the beam and he collapses on the ground. At Steven's order, the savages tie the guard up. Tor is dumfounded and there is awe in his voice as he marvels at Steven's accomplishment. He believes these strangers must be gods.

In the laboratory, Senta orders the Doctor - still unconscious - to be taken to the guest apartments to rest and recover. It is also busy work to keep the assistants occupied as Jano returns. The in-transference is about to begin, but Jano wants it kept secret for now.

The leader of the Elders seats himself in the transfer cubicle as he has done many times before. But he knows this is an altogether different procedure. When he is ready, Senta switches on. The energy collection jars bubble and empty while Jano's cubicle fills with gas.

In the cave, Tor is a changed man - happy and joyous in victory. However, his blood lust is unchanged as he wishes to kill Exorse immediately in retribution for all the harm that has been done to his people. Steven of course knows Exorse is more use alive and all the other savages agree. Steven is now ready to try and rescue the Doctor, but they must hurry. He cuts through Tor's protests and asks for a way into the city. Chal knows a way, but is worried about the guards. Steven is sure his light gun will be enough to take care of any opposition. They must try. Chal agrees and leads them off. Steven admonishes the others as he goes to guard their prisoner closely.

However, Tor is quick to grab a club as soon as Steven and the others are out of sight. He launches a blow at Exorse, but Nanina blocks it at the last moment and the blow is just a glancing one. When it is clear that she will not let him have his revenge, Tor tosses his club away and stalks to the other side of the cave. Nanina checks with Exorse to make sure he is OK. He remembers her as the last girl he brought into the laboratory and is surprised that she has treated him with kindness. He promises to remember that kindness.

Chal takes Steven and Dodo to the city. They hide behind some bushes and watch as a guard sits at his post before the entrance. It is one of the escape hatches the savages routinely use to leave the city after a transfer. The guards starts to eat something as he rests, obviously not expecting trouble here. Steven has no difficulty in catching the guard with his light gun, which actually knocks him out cold. Chal says this sometimes happens when the beam hits the victim's eyes. Chal shows Steven how to open up the door then drags the guards body into the bushes to keep it from being detected. There he will wait while Steven and Dodo go into the city to find the Doctor. Dodo picks up the stunned guard's light gun as she goes.

In the lab, Senta completes the in-transference but is alarmed when Jano does not respond to his voice. He opens the cubicle and help his leader out. However, Jano is fully alert and exits the cubicle on his own. But it is quickly clear that Jano has changed - he is not himself at all. He even stands differently, grasping both lapels with his hands and keeping his gaze upturned. He is grumpy and lashes out at Senta for fussing over him. The scientist is confused by this, but chalks the strange behaviour up to the effects of the full-power energy transfer. Jano admits he is not quite himself, referring to himself as not of this planet and referring to "his two young friends" Steven and Dodo.

Senta, blinded by scientific tunnel vision, does not realise what all this means. He leaves Jano alone, thinking he just needs rest after the experiment. But it is not truly Jano left in the lab. The leader of the Elders has absorbed not only the Doctor's energy but much of his personality as well. As soon as he is alone, he surveys the equipment around him with clear disgust. He picks up a piece of metal lying nearby and raises it over his head, preparing to smash the energy transfer equipment. Suddenly, Jano staggers, shaking his head to clear it. He drops the bar, realising what he has almost done.

Two personalities now inhabit Jano's body. But it is not clear who is speaking when he asks out loud, "What's happened to me?"

Steven and Dodo edge cautiously down the dim, featureless metal corridor, their light guns at the ready. Dodo's fear has resurfaced and she is concerned over the lack of guards. Getting in has been far too easy in her opinion. But Steven, more practical, knows the low regard in which the Elders hold the savages. Chal and his people are too scared to break in and one guard outside must be deemed sufficient. He urges Dodo onward.

But they have not entered unnoticed. Captain Edal is in the laboratory with Senta, who has returned. Together they watch Steven and Dodo's progress on a monitor. A little further and Edal knows they'll have no chance to go back.

Dodo stops Steven again, her nerves on edge. She doesn't want to continue. Steven is sympathetic to her fears, but he knows that this is their only chance to find the Doctor. But Dodo refuses to go, listening hard to some sound in the distance.

Edal is hardly concerned. He has a plan to get them further inside to the corridor. He calls to the guest apartments and orders the Doctor brought to emergency corridor U-3 right away. He is to be left there alone as bait for the others.

Dodo is certain from what she's heard that this is the same corridor she was in before. The t-junction just ahead leads to the laboratory. Steven is pleased and moves on. Dodo reluctantly follows, gripping her light gun tightly.

Edal receives a report that the Doctor is in position. Edal orders the guards to wait out of sight until they receive a signal from him.

Dodo and Steven reach the junction and turn the corner. They are both alarmed to see a shadowy figure ahead and Steven gets ready to use his light gun. They creep forward silently, peering hard into the gloom, but a familiar voice issues from the figure, a groan they would know anywhere.

Steven and Dodo rush toward the Doctor, who is slumped against the corridor wall, barely conscious. They bombard him with questions but he only groans in response. Not believing their luck - but not questioning it either - they pick up their friend and start to drag him to safety. However, they realise that they have been tricked when a metal door begins to slide closed just before the junction.

Steven hurries to the door and throws all his weight against it. It stays open, but only just, and he needs Dodo's help to keep it that way. Steven calls to the Doctor to move and go through, but in his depleted state he cannot move. Neither he nor Dodo can let go to help him and so they must give up. The door slides shut and they are trapped. Dodo looks sadly at the Doctor's hunched body, lamenting what has happened to him.

Edal, watching on the monitor, triumphantly orders his guards to go after the strangers. By filling the closed corridor with destructive vapours, the guards will be protected from the light guns.

In the corridor, the thick gas fills the area quickly. Through it, Steven and Dodo can see two guards approaching. The cloud stops their light guns from working so they are defenseless. As the gas reaches them, Steven and Dodo begin to cough. The guards wear masks and are unaffected. They continue to approach, their quarry pinned against the door.

Edal watches from the laboratory as his guards approach the strangers. Via a microphone he orders Steven and Dodo to throw down their light guns and surrender. Steven urges Dodo not to comply, but she knows they are beaten and doesn't want to die. She tosses her gun down, but Steven holds on to his, hoping he can still use it. Dodo begs him to surrender.

In the inner laboratory, Jano also watches events on a monitor. In the confusion, everyone has forgotten he is even there. In a whisper, he urges Steven not to give up his weapon. It is the Doctor speaking through him. Jano's hands move toward a set of controls beside him.

In the corridor, the door blocking Steven and Dodo's escape suddenly slides open. They react quickly, Steven holding the guards at bay while Dodo helps the comatose Doctor up and through. Once they are through, the door starts to close again. Steven fires his gun to keep the guards back and races through the door. It closes behind him, trapping the guards.

Inside the lab, Edal is livid. It is clear to both him and Senta that someone has aided the strangers' escape. While Senta raises the alarm, Edal heads for the inner laboratory to search for the collaborator. He is surprised to find Jano inside, standing by the control panel looking rather imperious. Edal accuses his leader of opening the door, but Jano ridicules him. Why would he aid their enemies? Jano will listen to no protests and orders Edal to prepare B Patrol to go after the escaped strangers. Edal is astonished to learn that Jano himself plans to lead the patrol.

Steven and Dodo have managed to get outside the city, dragging the Doctor all the way. They have gone some way into the scrubland, so far with no sign of pursuit. Chal appears suddenly from the bushes, startling them. He helps Steven take hold of the Doctor, marvelling all the while at their success. Chal knows just how to handle the comatose Doctor, having seen his people emerge from the city like this many times.

Chal assures Steven and Dodo their friend will recover in time. They must take him to the caves to rest. Even though he knows it is no longer safe, Chal is certain it is their only option. Steven is prepared to go until he hears the distant sound of footsteps approaching. The guards are on their way. Steven tells Dodo and Chal to take the Doctor while he tries to hold the guards back. Reluctantly, they agree and move off. Steven crouches down behind a nearby rock and readies his light gun.

Jano indeed leads the patrol, along with Edal. It is clear that the captain has not shed his suspicions about Jano as he watches his leader carefully. The group stops at a fork in the path. Jano orders Edal to take two of the men to the TARDIS' landing site in case the strangers are trying to reach it. He will take the other two to the Valley of Caves. Edal agrees this is a good idea, but only sends the two guards. He says he will stay with Jano's group...in case the leader needs help. It is clear that Jano is unhappy about this, but agrees. He leads Edal and the guards onward.

From behind his rock, Steven watches the small group come into view. He levels his light gun and prepares to fire. Ever wary, Edal hears a slight movement from ahead and shouts out a warning, pulling Jano to the ground. Steven fires and hits one of the guards squarely in the eyes, knocking him out. Edal and the other guard drag him into hiding where Jano already crouches.

Edal has worked out the direction of the shot and orders the other guard to go one way while he goes the other. He hopes one of them will be able to get behind their assailant and get a clear shot at him. Jano stays put. There is an eerie silence as the cat and mouse game continues. Unnerved, the guard fires off a wild shot in the direction of the rocks, but it passes over Steven's head. Edal, hearing the shot, fires also, with the same result. Steven, however, knows he's outnumbered and soon to be outmanoeuvered. Desperate, he lies flat on the ground and starts crawling back into the bushes.

Dodo and Chal continue dragging the Doctor. Dodo is worried about Steven, but Chal believes the young man's bravery will help him win through. Dodo is also concerned about the Doctor, but she expresses it as anger that he won't seem to help them as they go. Chal tells her gently it is not his fault. It is a side effect of the energy drain. They hurry on, nearly to the valley.

Edal and the guard circle around the rocks where Steven was hiding. They are sure they have him, but find that he is not there. Edal's anger grows, knowing that Steven is just trying to delay them.

But Steven has not gone far. From his new hiding place in the bushes, he fires his light gun. But Edal and the guard dive away at the last second and are safe.

Dodo and Chal at last come into sight of the caves, but Chal is very concerned to see no one outside. Surely there should be someone on guard.

But the entire group of savages is in the cave. There, Nanina continues to tend to the head wound Tor inflicted on Exorse. The group watches as Tor fumes, saying that people of Exorse's kind must be destroyed if their people are to have any hope of survival. But Nanina refuses this line of thought and continues tending to Exorse. Tor seethes, addressing the group and seeking support to have the prisoner killed. The other savages mumble assent but appear too afraid to speak for themselves. But Nanina is not afraid, reminding the others of Chal and Steven's orders to keep Exorse alive. Tor bristles, not trusting the strangers and even doubting whether Chal will return from helping them in their foolhardy venture. Nanina, fearing where this is going, stands and grabs a spear. She faces Tor down to carry out Chal's order, unafraid. Tor is taken aback at this, wondering how an enemy can mean so much to her.

However, before the two come to blows, Chal's voice calls from outside. Nanina goes to the cave mouth to help Chal and Dodo bring the Doctor inside. She hasn't forgotten her quarrel with Tor, but there are more important things to do first. She is worried by Steven's absence, but Chal assures her he will come.

Steven feels he has done all he can and breaks cover to run for the Valley of Caves. Edal and the guard fire at him from their vantage point but miss due to the bushes in their way. However, Jano has a clear shot at Steven as he runs. He levels his own light gun, but then hesitates. The Doctor's personality takes hold again and he lowers his weapon, unseen by Edal. The captain's anger flares anew, certain that the strangers will have reached the valley by now.

Indeed, it does not take long for Steven to reach the caves. He rushes inside. Dodo and the others are pleased to see him but their joy is short-lived. The guards are right behind him. Edal begins firing almost immediately. Steven fires back out the cave entrance and hits the second guard in the eyes. He collapses. Steven urges Dodo to move the Doctor to the back of the cave and to give him two of the energy capsules they used on Wylda.

Chal and Tor join Steven and they scan the area, looking for the remainder of the patrol. They detect movement in the distance - it is Jano, out of cover - and Steven prepares to fire. Suddenly the Doctor is at Steven's side and pulls his gun arm down. He tells Steven that he must not harm Jano under any circumstances though he does not explain why. Tor is angered by this, but Steven hesitates, giving Jano time to find cover again.

Dodo helps the Doctor to a resting place at the back of the cave and everyone gathers around him. The Doctor appears to be recovering his strength rapidly. Chal is angry at him for letting Jano escape, certain that his capture would have meant victory for the savages. But the Doctor has a plan. He refuses Dodo's suggestion to return to the TARDIS as he is determined to end the oppression of the savages. Convincing the Elders to treat Chal's people as equals will not work. He plans instead to destroy the laboratory and thus the Elders' power over the savages. Steven is stunned, thinking another trip into the city would be suicide, but the Doctor has that all worked out. All they need is one friend on the other side, which he believes they already have...

Outside the caves, Jano and Edal remain in hiding. It is rapidly growing dark. Jano orders Edal to return to the city, which the captain flatly refuses to obey. But Jano pulls rank and insists. He promises to return shortly with all the strangers as his prisoners. Edal agrees, but under protest. He leaves with the recovering guard, but his steps are slow.

From the cave mouth, Steven sees the movement. He knows that someone has left but he does not know who as it is too dark to see clearly. The Doctor tells him confidently that one person has been left behind but that Steven no longer needs to stay on guard. Chal questions him on this, but the Doctor tells him only that when it is fully dark, they will receive a visitor.

Edal returns to the city, his anger growing with each step, and hurries to Senta's lab. He tells the scientist all that has happened and that he is convinced Jano has changed somehow. Senta seems doubtful of this, even though he should know the reason why. But for some reason he is shocked as Edal tells two newly-arrived Elders that he believes Jano is about to betray them all.

Before long, as the Doctor expected, Jano arrives at the savages' cave, calling inside for the Doctor. Steven readies his light gun but the Doctor tells him to put it away. Jano enters slowly, almost dazedly. As if drawn here. Tor and some of the others hold their weapons ready but do not attack. The Doctor encourages them to trust Jano, telling them he comes as a friend.

Jano seems far from the confident leader he was. In fact, he seems lost. But the Doctor has the explanation for it all, an explanation that Jano himself would like to hear. The Doctor knew that Jano himself would take the in-transference of energy, and he knew what the result would beJano has received a measure of the Doctor's conscience and personality along with his energy.

The Doctor explains that Jano now sees the right and the wrong of things just as he does. And now he is an unstable element in a society which has built itself upon a moral wrong. Jano agrees with this, saying he has grown aware of the evil his people have done over the years. He says he is now determined to end it.

Chal is stunned by this and a little disbelieving. But Jano stands by his statement. He says he will be unable to persuade the other Elders to agree to his new way of thinking, but he has another plan. It is the same as the Doctor's.

While this exchange has gone on, Exorse has been working unseen to free himself. At last he manages to slip his bonds and he rolls to his feet and sprints through the cave mouth into the darkness. Steven recovers himself and fires the light gun, but Exorse is too far away. He has escaped.

Tor knows that if Exorse reaches the city and tells them what he has heard, their plan will be ruined. The Doctor is willing to risk this, but Nanina thinks she may be able to help. Without a word she runs from the cave.

Exorse picks his way carefully through the scrub in the dark. Shortly he hears the sound of hurried footsteps behind him. Fearing pursuit by the savages, he stops and picks up a piece of wood, intending to use it to defend himself. He is surprised as Nanina - all alone - appears before him. Her face is calm, her voice clear as she entreats him not to betray Jano's plan. His loyalties tested, Exorse responds that Jano himself is the betrayer, siding with the savages. But Nanina reminds him that they are not animals, but people just like him. She also reminds him - as he wavers - that she saved his life in the cave. If he speaks out, she and all her people will be condemned forever. In silence, his face a mask of conflicting emotions, Exorse drops his makeshift club and walks off into the darkness toward the city. Nanina does not follow.

In the laboratory, Edal has won over Senta and all the Elders now gathered there. Senta reinforces Edal's information by revealing the intransference of the Doctor's energy which Jano received. Edal moves to take command and orders a state of emergency. The assembled group is startled by his ruthlessness and quick dismissal of their long-time leader. At the cave, Jano and the savages, along with the time travellers, head off toward the city.

Some time later, Exorse has returned to the city and has been taken to Edal. The Captain interrogates the guard regarding his captivity. He wants to know if Exorse knows anything of Jano's whereabouts and of some plan he seemed to have in mind. Finally seeing his people for what they are, all of Exorse's doubts are erased. He says he did not see Jano while he was in the cave.

Jano and his group approach the entryway to the city. He urges them onward, holding them helpless in the beam of a light gun. It is a ruse for the sake of the guards, but it works.

Clearly Edal does not believe Exorse, certain he is hiding information. When Exorse insists he knows nothing else, Edal mocks him and orders him sent to the interrogators. Exorse is shocked; only the leader can order such drastic measures. Senta notifies him that Edal is the leader in Jano's absence.

But Jano is no longer absent. He enters the laboratory, much to Senta's surprise. Jano reminds Edal of his promise to return with prisoners, ushering in the large group of savages and all three time travellers. Senta's belief in Edal crumbles immediately and he tells his leader all that has happened, including Edal taking command. Jano orders Edal arrested and the guards obey. He is dragged away, demanding the right to have his say - a request which will never be granted.

Senta begins an abject apology, but Jano cuts him short, ordering the doors to the lab sealed. When no one obeys, Jano himself activates the control. The doors slide shut and Jano turns to address Senta and the gathered Elders. He tells them that what he has to say will be very hard for them to understand, as no one easily gives up the means of his power. He asks them to destroy the laboratory: "all the machinery which we have used to destroy ourselves."

Senta is shocked, not understanding. The savages are not their equals; they are incapable of development like the residents of the city. They are only on this world to provide energy for the citizens. Jano shakes his head sadly. He had had some hope that Senta might listen to him. That hope is now gone. He tells Senta and the others that the savages are their equals and that what has been done to them is wrong. He picks up a metal rod and raises it over his head, vowing to destroy the lab himself to stop the exploitation and make life on this planet better for all.

Senta activates an alarm and urges Exorse, the only guard in the room, to stop Jano. But Exorse hesitates and Jano begins smashing the equipment. Even though Exorse raises his gun, he cannot fire. And when Nanina appeals to him to help them, he lowers his weapon and joins in the destruction. The savages begin attacking the transfer equipment en masse, with the help of Steven, Dodo, and the Doctor. Senta is powerless to stop the destruction of his laboratory. Soon the energy vats are smashed and the entire practice of energy transfer is ended. The chaos recedes. The Doctor is very pleased to have contributed to the destruction of "something so evil".

Jano and Chal, knowing that victory is theirs, have already begun mapping out the new world that they must build. Somehow they must unite their two distrustful peoples. Jano thinks it may take a new leader to accomplish this difficult task.

However, the fight is not over yet. Edal and a group of guards have responded to the alarm and have managed to break down the lab doors. Edal orders the guards to seize Jano. But, stunned as they are at the destruction of the lab, they dare not lay a hand on their leader. Edal's gun is drawn, pointed directly at Jano. Edal's eyes are wild. Steven tries to reason with him, saying that even Jano's death could not now stop the change that is coming. But he only succeeds in angering Edal further.

Edal blames the Doctor for this chaos and is prepared to kill Jano to try and stop it. He moves to attack Jano, but Steven snatches up a light gun and knocks him out. Jano's life is saved, thanks to Steven.

The Doctor reminds Jano that hatred such as Edal's must still be overcome if the two people are to be united in peace. Jano believes they need a mediator to see that through until the people are one. He suggests the Doctor, but he graciously refuses.

Chal then suggests Steven, a notion with which Jano agrees. Clearly Steven is flattered, and more than a little tempted by this great opportunity, but he worries about Dodo and the Doctor as well as his own qualifications. But the Doctor assures him that he is the only right person for the job. Still Steven hesitates, wanting to be make sure that this offer comes from both sides. But when even the angry Tor agrees to abide by Steven's decisions, his reservations vanish and he agrees to stay.

Both sides seem very pleased, and Dodo hugs her friend with a mixture of happiness and sadness. Steven says he will miss her and the Doctor. Jano thanks the Doctor for all he has done - the "miracle" he has helped to bring about. The Doctor thanks him but does not let him forget the ruthless means used to extract his "wisdom". Jano and Chal head off to the Council Chamber to await Steven.

The Doctor is very proud of Steven but does not want to tarry over farewells. He gives the young man all the encouragement he can, then sends him off with a handshake. Dodo is near tears, but holds them back long enough to bid him goodbye. Steven heads off to the Council Chamber, saddened and excited all at once.

Dodo and the Doctor turn to go. Dodo wonders if they'll ever see him again. The Doctor tells her that in the complex web of time they travel, anything can happen. They head off for the TARDIS.