The TARDIS materialises on a bleak plain of sand and rock against a light clear sky and amidst a myriad of spaceships of varying designs. The ships are not relics and they did not crash here. They stand tall against the sky, but it is clear they'll never take off again.

Inside the TARDIS, the four travellers are still frozen and immobile. However, two things have changed. The column in the console is now dark and still, deepening the gloom, and the Doctor, Ian, Barbara, and Vicki are no longer wearing their 13th century crusading clothes. Instead they are all dressed - inexplicably - in their normal 20th century style. Slowly the group regains consciousness and mobility.

The Doctor turns on the interior lights and notes that they've materialised. Much sooner than he'd expected, it seems. Ian and Barbara are quick to notice their change of clothes and try to alert the Doctor. He, too, remembers them wearing "cloaks and things" from their last adventure, but seems unconcerned that none of them remembers changing out of them. He tries to turn his attention to the controls, but Ian and Vicki won't let the matter go. Vicki wonders where their crusading clothes went and the Doctor tells her to go and look as they're probably hanging up where they belong. As she goes, he asks her to bring him back a glass of water. Ian presses the issue, wanting an explanation, but all the Doctor will say in answer is "time and relativity".

Shortly, Vicki has found the clothes hanging in the wardrobe and the Doctor is satisfied. She is still confused, but nonetheless Vicki goes to the food machine to fetch water for the Doctor. A few buttons and the machine produces water in a glass which she picks up and starts to carry. However, she hasn't got a good hold on it and it slips from her hand and shatters on the floor. To her shock and amazement, the glass immediately comes back together and leaps back into her hand, completely intact and full of water.

The scanner is working and the Doctor, Ian, and Barbara survey the panorama of spaceships outside. Ian and Barbara think it could be a launch pad or a graveyard, but the Doctor knows that all of the spaceships come from many different eras. They were placed together for a reason. In the distance they spot a building, but it gives no clue as to the nature of this place. The Doctor says he would like to go out and look around, noting that the readings show it to be quite safe. Barbara reminds him ruefully that the readings don't always tell the whole story.

Vicki joins them and the Doctor takes the glass from her hand and drinks. Her expression is one of grave concern. The Doctor has heard the shattering of the glass and thinks she is concerned because of it. He assures her it is quite easily replaced, but she tells him that will not be necessary. He's holding the "broken" glass. She explains what happened. The Doctor's face turns serious as he studies the glass, assuring Vicki that he believes her. She isn't sure he's being honest and tries to convince Ian and Barbara too. They find it difficult to accept.

Their conversation is interrupted by the Doctor, who announces that he has studied the scanner picture and realised where they area space museum! The ships out there are arranged in quite a natural progression of sophistication, to show a timeline. His companions are excited about the prospect, Ian however noting that someone must be in charge of it. The Doctor agrees, looking at the glass again and saying that there are several mysteries they need answers to. They should go outside and try to find those answers. He opens the doors and they venture out, Ian in the lead.

Ian notices the pervasive layer of dust over everything and resurrects the possibility of this being a graveyard. Everything looks lifeless. The Doctor locks the TARDIS door and goes to examine some rocks that Vicki has seen. He is amazed at the level of erosion evident. It is very advanced and points to a long-dead planet. Ian is confused as he's always associated large-scale extinction with extreme cold, yet the atmosphere here is quite pleasant. Barbara suggests it might get colder as darkness approaches, but the Doctor is uninterested in guesses. He wishes to go in search of the answers to the mysteries here. He urges them all to stay close together, a point which must be stressed with Vicki. The Doctor starts to head off toward the building they saw earlier on the scanner, but Ian stops them all with an observation.

They have been walking around on a thick layer of dust covering the ground but seem to have left no footprints at all. The Doctor says rather mildly that it is a curious phenomenon, but his face betrays greater concern.

It does not take the group long to reach the main building. Ian and Barbara look it over and find it quite extraordinary. It is several storeys tall and circular, its floors stacked up like layers on a wedding cake. The outside walls are 3-dimensional and geometrically patterned. They have found the only doors and they are firmly shut. The Doctor notes that they've seen no beings on the way, seeming grateful for that fact. He turns his attention to the doors.

Barbara stops them all, very concerned over an observation she has made the utter and complete silence on this planet. When they stop talking, there are no other sounds - nothing at all. She describes it as a silence you can almost hear, and Ian again likens the place to a graveyard. The Doctor tries to stop this alarmist talk, but is stopped midsentence when the building's doors slide open suddenly. The four travellers dodge out of the way, looking for a place to hide as there are two men coming toward the exit from inside. But all they can do is press themselves against the wall and hope they haven't been seen. Unfortunately, Vicki begins to sneeze and Barbara hurriedly stops her. The group remains silent until the two men - fairly normal-looking humanoids dressed in identical white uniforms - fully emerge. It is then that Vicki's ill-timed sneeze finally breaks out, shattering the silence. But the two men carry on walking, oblivious to the presence of the strangers.

Vicki apologizes for nearly giving them away, but no one seems concerned. What is more extraordinary is that the men didn't seem to hear the sneeze at all, even though they were mere feet away. For the moment, the Doctor chooses to count themselves lucky and decides to take advantage of the fact that the doors to the building now stand wide open. He leads the others inside.

They find themselves in a large atrium area, the ceiling high above and all of the walls simply blank metal. Barbara notes a lack of windows and the Doctor believes this is meant to keep out the strong erosive agent in the atmosphere. For this is, as he thought, a museum, filled with artefacts of historical value. Along the walls are numerous pedestals and stands with fantastic gadgets and machinery. They disappear down every corridor, all of which look endless. It is set up very like museums on Earth. Ian realizes the two men they saw must have been guards and the Doctor warns an inquisitive Vicki to keep her hands to herself in this museum. Ian wonders who could have started all this, but the Doctor has no idea. He suggests they venture further inside in search of the answers.

The entire group is stopped cold as they turn a corner and come face to face with a Dalek! They all relax when they realise it is dormant - simply another exhibit in the museum, complete with identification marker. Vicki reaches out to touch the creature, fascinated to finally see one, but the Doctor stops her. She knows from her history lessons that the Daleks invaded Earth 300 years before her time, but had no real idea what they looked like. She thinks this one looks quite friendly! Ian tells her they met the Daleks during their invasion of Earth and the Doctor and Barbara join in to let her know they are most definitely not friendly.

Whilst Ian utters the hope that they will not be unfortunate enough to meet the Daleks again, the Doctor's gaze wanders back out into the atrium. Suddenly he springs into action, herding the others very quickly to a hiding place behind a display case. He has seen two young men enter the atrium, headed this way. The young men - boys really - enter the room. Like the others earlier, they are normal looking humanoids but with steeply upswept eyebrows and wearing plain black work clothes. They appear to be speaking to one another somewhat urgently. However, no sound escapes their lips. One of the boys glances furtively back out into the atrium, exchanges words with his comrade, and then leads the other back out into the depths of the building. All of this without uttering a single sound.

Ian goes quietly to the door to look out and make sure they are gone. When they are sure they are alone, they discuss incredulously what just happened. Ian wonders if the people here speak on some higher frequency, but the Doctor doubts that theory very much. Alone for the moment, he leads them all deeper into the museum. Ian expresses the opinion that the two boys did not seem at all hostile, but Barbara isn't sure appearances can be trusted. And, unless one of them can lip read, they shall never be able to find out for certain anyway.

During this exchange, Vicki has wandered to the other side of the room where she has found an exhibit which interests her. Like all young people in museums everywhere, Vicki cannot resist the urge to touch the exhibits and tries to do so now. Amazingly, her hand passes right through it as if it were thin air. She snatches her hand back quickly and calls for the Doctor. Her agitated voices draws Ian and Barbara as well. The Doctor starts to scold her for touching the exhibits, but Barbara stops him when she realises how upset Vicki is. Ian duplicates her feat, his hand passing through the entire machine. Although they can all plainly see the item, it is obviously not there at all. His companions are baffled, but the Doctor is nearer now to putting all the pieces together.

Ian notices sudden movement behind them and alerts the others. The two black-clad young men have returned with a third. The travellers look desperately for somewhere to hide, but they are at the far end of the atrium, completely exposed. The Doctor orders them all to stand perfectly still right where they are and to keep silent. The boys exchange a brief conversation, all the while scanning the atrium for someone or something. They walk past the travellers, only inches away, turn and look past them, and then leave the building through the main doors. As before, they make no sound even though their conversation is constant.

Alone again, the travellers unfreeze. All of them are dumbstruck by what happened. There is no way the boys could have missed seeing the strangers in their midst. With strange clothing and looks, surely the boys would have made some gesture of recognition. The Doctor has never seen anything like it before and Ian spells it out: the travellers are invisible to the people on this planet. That settles it for him, but the Doctor points out another possible explanation: they are not really here at all.

Some time later, the travellers are deep into the museum, having traipsed for ages through room after room of similarly alien exhibits, Vicki for one is very tired of it, certain that the answer to the mystery can't possible be found here, but the Doctor is determined to press on. Moving into the next room, though, the Doctor is proven right. For there before them is the TARDIS! It is on display like everything else here. While Ian, Vicki, and Barbara can't understand why it is here, they don't much care. All of them suggest piling into it and leaving immediately. But the Doctor knows that this is impossible. He reaches out and his hand passes through the TARDIS. It is as intangible as all the other exhibits.

For the Doctor, this gives him the answer to the mystery. Despite what his companions may think, they are not really in the museum at all. And the TARDIS is not in two places at once. Looking over their shoulders, he directs their attention to the far wall. There, to their mutual horror, they find themselves! Not models or mock-ups or waxworks, but their physical beings standing in glass cases gazing lifelessly outward. Ian, Barbara, Vicki, and the Doctor see themselves as specimens in this space museum.

Strangely, it is Vicki who offers a partial explanation, telling them all that time - like space - has dimensions of its own that can exist simultaneously. They are in the cases in one dimension, and looking at themselves in the cases in another. The Doctor is impressed, but Barbara is horrified. This ties together all the strands of the mystery. As the travellers are not really here, they cannot leave footprints or break glasses or touch things. The only way in which they are really here is in those cases.

But knowing what is happening puts them no closer to getting out of it, especially as the Doctor admits that the complexities of the fourth dimension have always caused him problems. He speculates that the TARDIS somehow jumped a "time track" which put them here. And the way out, he reasons, is very simple. They have ended up in their own future. Before they ended up in the cases as exhibits, they had to have properly arrived here in the TARDIS, been found by the people here, and captured. For some reason they were deemed worthy subjects for exhibition and put in the cases. They are seeing - from their perspective - a possible future and for them all the events which lead up to this fate are still yet to come. Everyone now understands.

Vicki thinks they should all just pile into the TARDIS and leave here immediately, but the Doctor says no. The only way out of all this is to wait here until they properly "arrive". By running away they do nothing to alter their future and almost ensure they will end up as exhibits forever. Ian wonders how long it will be before they "arrive", but the Doctor does not know. He cannot measure the extent of the time track the TARDIS jumped. But the exhibits all show them wearing the exact same clothing they are now wearing, suggesting that it shouldn't be long at all. They will know they've "arrived" when the cases disappear and they all become visible to the people here. And from that moment on they will all be in great danger. They must do everything in their power to keep themselves from being turned into specimens in the space museum.

It is a mere few seconds before Barbara and the others feel something strange happening. They all get colder and relive in flashes their departure from Palestine, their flight, their arrival here, and the breaking of the glass. The travellers freeze once again.

Outside, the two men in white uniforms discover the TARDIS and the footprints which have appears in the dust.

Inside the museum, the phantom TARDIS and the exhibits of themselves vanish. The Doctor and his friends slowly come to. They now feel the coolness of the atmosphere, which they could not before, and they hear real background sounds. Barbara is the first to notice that the cases are now gone.

In the office of the museum's coordinator, the guard commander announces to the coordinator, a man called Lobos, that he has finished repairs on a piece of equipment. One of the clasps had broken due to the corrosive effect of the atmosphere. With a long-suffering sign, Lobos says it is like everything on this planet - wasting away. He feels it himself. He is older than the commander but moves slowly, like a much older man. He is a Morok, not only coordinator of the museum but also governor of this planet - Xeros. The Moroks conquered Xeros long ago and now lord over the inhabitants here. Lobos volunteered for this assignment to escape the boredom of his life on Morok. He has only 2000 Xeron days left in his rotation and he can't wait to go home, even though he is not certain what he'll do with himself once he gets there. With another deep sigh, Lobos sits back at his desk to begin the thrilling task of filling out reports.

Suddenly the door slides open and the guard commander of K Division enters. Lobos is angered at the lack of respect but listens as the man tells of the discovery of the alien craft outside. His men have tried to enter it but failed. He is certain the aliens are loose on the planet, three of them at least. Lobos seems almost gleeful at this intrusion - at last something interesting is happening. He alerts B Division to be on the lookout for the intruders. The guard commander worries that "the rebels" may also be looking for the strangers but Lobos laughs this off. These "rebels" are mere children and pose no threat to Morok might. If they ever do, he will crush them. As for the aliens, Lobos wonders if they may be suitable specimens for his museum...

Elsewhere on Xeros, two of the black-clad young men wait in what appears to be a disused storeroom. They are Xerons - the rebels who seem of so little consequence to Lobos. One of them, Sita, checks the hallway outside and nervously informs his comrade, Dako, that there is no sign of their friend Tor. They know he managed to contact the rebel group in the next sector, but he is late in returning and they fear he may have been captured by the Moroks. Dako is particularly worried, believing as he does that Tor's plan to wait and hide until the right moment comes is the wrong approach. Even though the Moroks are armed and the Xerons are not, he believes they should strike now before they are all rounded up while waiting in vain. Tor arrives in time to overhear this last comment and reiterates his strategy with calm conviction - they will get only one opportunity to strike at the Moroks and they must wait until they have a better chance of success. This seems to quiet Dako for the moment.

Tor explains why he was delayed: he has learned of the arrival of the alien spacecraft and the search that has been organized for its crew. The newcomers are clearly not allied with the Moroks and likely know little or nothing about Xeros and its conquest by the Moroks. Tor is certain these aliens will have weapons or will be of some other assistance to them, if they can locate the aliens before the Moroks do. They must at least try. All three young men head off to start their own search.

In the museum, Ian, Barbara, and Vicki have disregarded the Doctor's instructions and are in the process of opening a display case. Inside is an energy weapon that looks brand new. Ian removes it and helps the others close the case. He hopes it works and brandishes the small rifle in a circle. The Doctor admonishes him for playing cowboys and Indians whilst they have a serious problem and asks him to put the gun back. But Ian plans to keep it, even if it's just useful for bluffing their way out.

Barbara wonders whether they even want to try to get out. They must do whatever they can to break the chain of events leading to their capture and imprisonment as museum exhibits. Going outside might be just what they're not supposed to do. The Doctor concurs that they don't know which path is right and which is wrong, but they must choose some course of action. Vicki naively thinks that getting out of the museum and leaving in the TARDIS would be enough, but the Doctor knows this is not the case. Simply changing locations will not alter the future they have seen. The Doctor wanders off to contemplate their next move, concentrating on the question of who would want to make exhibits of them in the first place.

Barbara is certain they should stay here and hopes the Doctor will come to the same conclusion. Vicki notices that Ian has lost a button on his jacket and the Doctor finds this very interesting indeed. Ian wonders why and the Doctor notes that many great discoveries have resulted from attending to the smallest detail. Like the man who observed the steam from his kettle. The Doctor cannot recall his name even though he himself was there when it happened. Barbara supplies the famous man's name: James Watt. The Doctor assures Ian that a lost button can change the future and chides him for not noticing whether the exhibit version of him had all its buttons. After a moment, the time for pondering is over. The Doctor decides that they should try to leave the museum and get to the TARDIS. From there they can try to stop it (and them) from being turned into exhibits. The others agree and they are off.

However, they find themselves unable to agree on which direction to go. It becomes very clear that none of them can retrace their route with any certainty. Unable to agree, the Doctor chooses Vicki's directions and they set out again. Turning right into a corridor, Barbara finds it all unfamiliar. Vicki expresses confidence despite Ian's scepticism. The Doctor joins in, agreeing with Vicki. His confidence returns and, prodded by Vicki, he leads them onward. Ian and Barbara take a moment to share a laugh at this false bravado, even though they know they are still in danger.

Lobos receives a report from the commander of K Division that the alien spacecraft has been secured. The footprints led them to the museum where the search is focusing, although the aliens have not been spotted yet. Lobos is pleased with this report and awaits news of the capture of the intruders.

Vicki leads the travellers onward. Barbara thinks the place mazelike, but Ian is confident they will find an exit. The Doctor orders them all to stay quiet from now on. They do not have the luxury of invisibility now.

Behind the group, Tor, Dako, and Sita emerge from round a bend. They are surprised to have found the aliens so quickly and to see them walking so brazenly through the museum. They duck back into the corridor to discuss their options. The nervous Dako was quick to notice the gun that Ian carried and now doubts very much that these people are friendly. Despite his optimism, Tor is forced to concede this possibility. He suggests capturing either the girl or the old man and explaining their plight. Hopefully they can win over their "captive" and this will help them gain the trust of the entire group. Sita and Dako agree and they hurry off to intercept the strangers.

As they turn into a new corridor, the Doctor and his group are moving slowly, watchful for guards. However, the Doctor's scientific curiosity gets the better of him and he stops to examine a piece of machinery on display. Ian scans the area and finds it clear, so he leads the others onward. Vicki stops to urge the Doctor to follow and she goes off round the next corner. The Doctor is left alone with the fascinating piece of equipment. He finishes his examination a moment later and straightens up to go. Suddenly a door behind him slides open and he is grabbed and hauled inside another room.

Dako, Sita, and Tor stand over the Doctor a moment later. He is lying sprawled on the floor, his eyes closed. Dako thinks he may be dead, but Sita is sure he only fainted. In truth, the Doctor is very much awake, pretending to be unconscious. Tor believes they cannot wait for him to come around and so goes off with Sita to find something to rouse him. They leave a worried Dako to watch over the Doctor.

Meanwhile, Ian, Barbara, and Vicki have noticed the Doctor's absence. Ian and Barbara are quite alarmed, Ian badgering the girls to try and remember where they last saw him, thinking he just took a wrong turning. Barbara will not take the blame for this and she and Ian quarrel. Ian admits he's most angry at the Doctor for wandering off and Barbara admits it's possible they left him behind. Vicki simply figures he's been captured, a notion the others vehemently reject. Nerves are on end, afraid that Vicki could be right. They try to decide what to do next and which of their choices is the sure way into those cases. Ian finally suggests they continue on, trying to find a way out. Barbara agrees and a relieved Vicki leads the way again. All this talking and arguing was starting to get on her nerves.

Tor and Sita return to the room to find the Doctor gone and Dako bound and gagged on the floor. He didn't see or hear anything before he was attacked from behind. He's not even sure it was the old man who knocked him out. Tor believes it was him and that he's gone to rejoin his friends. The three of them will have to find him before he does or face confronting the entire group. They must do something quickly or the Moroks will find the aliens first.

But the Doctor has not gone off to find the others yet. In fact, he is hiding very nearby - inside the Dalek casing on display! He is inordinately proud of his trick.

Once the Xerons are gone, the Doctor climbs out of the Dalek and heads out into the corridor to find his friends, still chuckling to himself. Unfortunately, two Morok guards have just passed through the corridor and are still close enough to hear him. He quickly finds himself facing two armed men. He is now a prisoner of the Moroks.

Some time later, Barbara begs her friends to stop walking and rest. They stop near a set of metal pylons which reach to the ceiling. It is a distinctive feature and they all know they've passed it before. They are going around in circles and, Ian points out, getting nearer and nearer to ending up in the cases. But his despair leads him to an idea. He pulls Barbara's cardigan from her shoulders as he reminds them of the myth of Theseus and the labyrinth. He plans to use Barbara's sweater as his ball of twine to keep them from going in circles. He and Vicki start pulling on the cardigan to rip it and start a thread, but Barbara is a little put out about not being consulted on the use of her sweater. Vicki realizes that if anyone sees their trail they can find and catch them, but Ian thinks it is a risk they must take. They'll be captured anyway if they wander aimlessly for much longer. He continues to attack the sweater without success. Barbara takes it from him, along with his penknife, and reluctantly starts to dismantle her cardigan.

The Doctor finds himself trapped in a very small, circular, windowless chamber. It appears to have no doors and only a chair for furnishing. A bright light burns from beneath the perspex chair. Tired from all this exertion, the Doctor decides to sit for a moment. When he does so, a metal clasp closes round him, trapping him in the chair.

Tor, Dako, and Sita are the first to come across the thread trail. They can't figure out why it is there but know that they can use it to find the aliens. They set off again.

In front of the Doctor an entire section of wall slides away to reveal Lobos sitting at a table. He seems rather genial as he welcomes his guest to Xeros. The Doctor at first refuses to speak, but Lobos goes ahead and introduces himself as governor. The Doctor belittles this, calling him nothing more than a curator. Lobos tells him that this museum is a memorial to the might of the Morok Empire, but the Doctor notes a distinct lack of interest in the place. Lobos agrees somewhat, telling him that it was once well attended but that years of superiority has lessened the Moroks' interest in their heritage. They get few visitors now. The Doctor flippantly suggests lowering the admission price and Lobos laughs at this joke, pleased at the chance for some witty repartee. But he actually explains the situation. Many years of superiority and a lack of new conquests has made the Morok people lazy and inclined to rest upon their laurels and simply enjoy the good life. The Doctor likens it to the decline and fall of the Roman Empire and finds the familiar story rather tiresome.

The Doctor reveals that he is an explorer and a scientist and Lobos believes he has found a kindred spirit, something he has sorely missed here. The Doctor is less than enthusiastic about this and refuses to answer anymore questions. Lobos drops the pleasantries and informs the Doctor that he can get the information he wants with our without his cooperation. When Lobos asks him where his companions are, the Doctor does not answer. However, Lobos looks at a display screen next to him and then informs the commander of B Division where to find the other aliens and describes them in detail. The Doctor's superior smile vanishes, replaced by a steely unreadable gaze.

Lobos explains that the chair in which the Doctor sits is attached to a mental imaging device. By asking questions, a picture forms in the subject's mind which is relayed to the screen. The Doctor will give him answers whether he speaks or not. However, when the next question is asked - how did the Doctor arrive on this planet - a surprise awaits Lobos. The picture on the monitor is that of a pennyfarthing bicycle! Lobos doesn't know what it is but knows it is not a spaceship. The Doctor laughs at the governor's consternation.

Elsewhere in the museum, Ian plays out the last of the thread. They can no longer leave a trail, but at least it worked while it lasted. They have not retraced their steps but are in a part of the building they do not recognize. Barbara starts to despair that they cannot escape their destiny, but Ian rejoins her and Vicki with good news. He leads them round the corner and they are in the familiar atrium, entering from the side opposite of where they started. Overjoyed, Ian throws open the doors. Instead of freedom though, they see the TARDIS, surrounded by a group of guards, being muscled toward the entrance.

The Doctor challenges Lobos to continue the questioning. In response to the question of the Doctor's origin, a picture flashes up of seals frolicking in the sea. The Doctor calls them "old friends". Lobos seethes with anger, noting that the Doctor is not an amphibian like the creatures on the screen. A picture of a dandy in a bowler hat angers Lobos further, as does a report from B Division that there is now sign of the aliens in the corridor they searched. Lobos angrily orders a priority search. But the Doctor tells him not to blame his men. The picture Lobos saw was an old one - from the last place he saw his friends. They have clearly moved on since then.

Lobos is suddenly in no mood for the Doctor's sense of humour and tells him he is of no further use. He will be turned into a museum exhibit. A picture forms in the Doctor's mind and is relayed to the screen - the Doctor himself frozen in a glass case. Lobos regains his composure when he realises he has rattled the Doctor. He calls two guards who immediately take hold of the Doctor. They are to take him to the preparation room.

Barbara and Ian watch through the cracked main doors as the guards move the TARDIS. Barbara is concerned they might damage it, but that is really the least of their worries. Ian moves over to let Vicki have a look. They've now stopped moving it and have set it down outside the main doors. Ian agonizes over what to do next to change their future. He suggests trying to find the Doctor.

Vicki thinks one of them should stay near the TARDIS to keep an eye on it, but Barbara points out they know where it's headed. If it becomes a display in the museum, their future will be assured. Ian laments the nightmare they've landed up in but that just makes Barbara angry. They need to take some kind of action! Ian protests that they can't do anything without more information and it looks like the two will start arguing again. But Barbara stops when she hears a commotion outside. They all rush to the doors.

Outside a group of Xeron youths has gathered around the TARDIS, trying to examine it. The Guard Commander drives them away angrily, then turns to his subordinates. They tell him there is no way in to the box and he takes it very personally indeed. As with everything that goes wrong on this planet. Lobos will blame this failure on him as well. The long-suffering Commander tells his men he has little to show for being the Governor's scapegoat for so long. Out of frustration, he slaps the side of the TARDIS.

Suddenly the soldiers snap to attention and the Commander turns to see Lobos himself approaching. All is silent as the leader examines the strange ship. He finally comments, saying it must be very cramped indeed with four people inside. He casually tries the doors, expecting them to be open. He in surprised and angry when they are not. As expected, he turns on the Commander, berating him for not forcing it open. The Commander in turn blames one of his men for disobeying his order to bring the cutting equipment, an order everyone knows was never given. The soldier's protest is silenced and he hurries off to comply.

The Commander apologises for the incompetence of his men and inquires whether any of the aliens have been captured. Lobos tells him of the Doctor, a fact which the Doctor's friends overhear and note well. Lobos berates the Commander for his laxness in not finding the others yet, calling his guards half-witted amateurs. He vows to tighten discipline all round when this is over.

Inside, Barbara notes that the talking has stopped, hoping the soldiers have finally gone. As all 3 travellers move around for a better look outside, they do not notice a guard entering the atrium behind them. He looks weary and more than a little disinterested, but he draws his gun nonetheless and approaches, ordering them to stay put.

Startled, the group turns, their fate uppermost in their minds. The guard takes the rifle away from Vicki, keeping a bit of distance from the group. Ian makes a move toward the guard and is ordered to stop. Barbara agrees, afraid Ian will be killed. But Ian believes that the guard can't kill him. If he did, then the future would be changed. Barbara agrees, but reminds him that ending up dead is just as bad as ending up as museum displays. Ian is angered again, realising that they dare not do anything for fear of their future. They debate this point heatedly for a moment, but come to the same conclusion: they must choose some course of action and follow it, right or wrong. Second-guessing themselves is clearly not working. Ian decides they must find the Doctor and sets about dealing with the guard.

Ian slowly advances on the startled guard, refusing to come along quietly as ordered. He ridicules the guard's threat to kill them all, badgering him to admit that he has no orders to kill. In fact, his superiors will probably be angry indeed if the fugitives are not captured alive. All the while, Ian has continued moving forward, the guard falling back a step at a time. Finally, Ian makes his move, knocking the guard's gun aside and grabbing him. The two men struggle and Ian urges the women to run.

Outside, Lobos and the guards hear the commotion and burst inside the museum. Vicki and Barbara are forced to flee back into the museum, chased by more guards. Ian is subdued by a second guard and Lobos orders him taken to his office. He joins the pursuit inside.

But Ian does not give up. As he is dragged outside, he renews his struggle and throws off the two guards. A fight ensues and Ian manages to disarm and bet up both men. He runs off into the wasteland.

Barbara races down a corridor, far ahead of her pursuers for the moment. She spots a closed door and opens it to go inside a small dark room. She calls to Vicki to join her, but the girl is nowhere to be seen. She leaves the door open for the moment and ventures inside the room. She is startled by what appears to be a person watching her from the shadows, but it turns out to be a display model. This is a storage room of disused exhibits, full of dusty cases and display pieces. Footsteps echo down the corridor and Barbara hurriedly closes the door. She hides behind a packing case. A guard enters partway and looks around briefly. Barbara circles round the case to stay out of sight. His comrades are eager to continue pursuit and so he leaves, certain no one is hiding inside.

Barbara comes out from hiding, relieved that she has evaded capture for now. She is ready to try and reach the exit and the TARDIS again, but finds to her horror that the guards have locked the door behind them. She is trapped inside.

Vicki also is ahead of the pack, but she is tiring quickly. She stops to rest for a moment, her back to the wall and her gaze wary. She doesn't hesitate long, knowing she must keep on the move. However, the wall she sidles along has a doorway in it. From inside, a pair of hands grab her and drag her into a small anteroom.

Inside, Tor, Dako, and Sita try to get her to trust them. They insist they are nothing like the evil Moroks and would like to defeat them. Vicki is full of questions, questions Tor would rather answer when they are safe in hiding. Vicki realises these are the people who captured the Doctor and she tries to run. She doesn't get far and Tor tries to explain what happened with the Doctor. Vicki is still wary but is gradually being won over by Tor's concern for her friends.

She explains that Ian was being held by the guards and that Barbara took a different turning as they ran. She couldn't turn back to join her. Tor thinks Barbara must have ended up in the storerooms and sends Dako to find her. He and Sita will take Vicki back to their HQ where she will be safe.

Lobos and the Commander exit the museum some time later, livid at the guards' failure to find the two women. Lobos sees the two guards standing helplessly by the alien ship and knows immediately what has happened. The man has escaped as well. Lobos' anger grows, but he knows that an all-out search in the museum will take too long. He decides to take matters into his own hand, ordering the Commander to withdraw all guards from the building. They are to search for Ian in the wasteland. He will deal with the two women in a different way. He leaves one guard on the TARDIS and stalks back to his office, the Commander trailing timidly behind.

But Ian has not gone far. In fact, he is hiding behind the TARDIS. Once the others are gone, he sets about capturing the lone guard on the TARDIS. He tosses a stone to distract the man and get him facing the wrong direction. In short order, Ian sneaks up behind him, grabs his gun arm, forces the weapon from his hand, and points it at the man.

The demoralised guard, never expecting to see action like this on a museum posting, is an abject coward, begging not to be killed. Ian uses this to his advantage. He discovers that whilst the Doctor is a prisoner, he is not dead. He has been taken to a place called the preparation room. From there he will be turned into a museum specimen through a process similar to embalming. Despite the terrified guard's insistence that nothing can be done to reverse the process, Ian is determined to get to the preparation room. The guard will take him. The man tries to protest, but the look on Ian's face and the gun in his hand prove that he is serious indeed. The guard leads the way.

Lobos returns to his office. He is surprised to find a directive from Morok on his desk. It seems there has been a change in policy toward the Xeron youth. They are now seen as a threat to be eliminated. This pleases Lobos, but he is more afraid now that the rebels have made contact with the aliens. He also learns that the guards have nearly finished withdrawing from the museum and moves ahead with his plan, which he hopes will deal with both threats at once. One hour from now, the main museum building will be sealed and the air replaced with zaphra gas, a nerve agent. Anyone still inside at that time will be driven out or will be permanently paralysed.

Barbara meanwhile has found a metal bar with which she tries to force open the storeroom door. She has no luck and remains a prisoner inside.

Some time later, she rests on the floor, propped against a wall. She is nearly asleep when she is startled by footsteps outside. She hides behind the case again as the door slides open and someone enters. Desperation settles over her and she picks up the metal bar, ready to attack whomever has entered. However, just as she rises to strike, a young man's voice calls her name. It is not a guard, but one of the black-clad youths they saw before. And he knows her name. Barbara is taken aback and stops to address the boy.

Tor and Sita have managed to get Vicki safely to the exit. They are aware that they've seen no guards, but don't seem to be concerned about it. There is no guard outside either, even in front of the TARDIS. Vicki wishes to wait for Barbara and Dako, but Tor tells her it is far too dangerous. Dako knows to head for their HQ. The three head off for safety.

Dako has explained everything to a sceptical Barbara, insisting that his people are friends. But Barbara is hard-pressed to believe him. She keeps her makeshift weapon at the ready. Dako continues, telling her how the Moroks subjugated Xeros and made this museum, a shrine to all their wars. Xeros was a place of peace and harmony and knowledge. The Moroks conquered them without much resistance due to their superior weapons. The peaceful Xerons were no match, but Dako promises that they will soon rise up and defeat the Moroks. Barbara is still sceptical, but she is beginning to believe him. Dako knows they need to get moving quickly. He promises to get Barbara safely out of the museum and they turn to go.

However, gas is beginning to pour into the storeroom. Dako thinks there is a fire, but Barbara knows better. Both of them begin to choke on the poison. She covers her mouth and nose with a handkerchief and encourages Dako to do the same. Then she takes the initiative and heads out of the room, Dako right behind her.

In the Xeron hideout, Vicki learns more of the history of the Xerons over refreshments. Tor tells her that the Moroks destroyed most of Xeron civilisation when they invaded and enslaved the remaining population, mostly children. As the children grow up, they are taken to other planets in the Morok Empire. Tor, Dako, and Sita are all due to go soon. So they hide here and plan. Their life of slavery makes it very hard to organise any form of resistance. Vicki is confused, having noted the small number of Moroks apparently here. She is shocked to learn that the Xerons outnumber the Moroks, but that the Xerons are weak, disorganized and unarmed. The small Morok garrison is more than enough to keep control. Sita takes Vicki's shock as ridicule and he angrily leaves the table, painfully aware of the pathetic state of their "revolution".

Tor asks Vicki how she and her friends came to be here and she is embarrassed to admit it was an accident. Tor thought as much - no one comes her out of choice. Sita, standing gloomily nearby, breaks through their attempt at small talk, telling Vicki he's certain Barbara's been captured. Tor tries to reassure her, but Vicki is sick of hearing plans with no actions to back them up. She is talking about more than just Barbara and Dako, she is talking about their pathetic "revolution", which really just amounts to making a nuisance of themselves.

Tor tells her there is nothing they can do without weapons and Vicki stands decisively. If that is what it takes, that is what they shall get. Sita accuses her of being the dreamer now, but Vicki is resolute. They must take the Moroks' own weapons - a true revolution. But Sita and Tor tell her they have tried this in the past. Once gun can do very little against an army; besides, the Moroks take Xeron hostages until the gun is returned. Vicki learns that there are numerous weapons kept in an armoury, but she is unsure if these young men would even know what to do if they were armed. Tor assures her that with weapons, all their planning would pay off quickly.

But Tor despairs, as they have tried to gain entry to the armoury before. It is generally poorly guarded, but its lock is controlled by a sophisticated computer which asks questions. The door opens only to the truth. Vicki is intrigued, thinking she may be able to open it, and wishes to go immediately. Tor and Sita are pleased to take her, feeling a surge of hope long missing, but they wonder why she seems so keen for their revolution to succeed. She tells them only that she has her own reasons for "wanting to see the future changed". They hurry off.

Ian and the guard reach the main administration building. Ian is ready to go in, but the guard hesitates. If they wait until later, there will be less guards on duty and it will be easier to get in. Ian wishes to press on now, but is forced to hide when he hears someone approaching. He is still within sight of the guard and keeps his gun pointed at him to ensure cooperation.

It is the Commander approaching and the guard stands at attention. He concocts a story about being summoned by the governor, although he is forced to admit he left the alien spacecraft unguarded. The Commander, weary of Lobos' unfocused governance, believes this story and he heads off to see about getting another guard on the TARDIS. Prompted by Ian, the guard asks his commander if the two women have been recaptured. The Commander tells him the zaphra gas will soon drive them from hiding. Then he is off. Ian emerges, praising the terrified guard for his quick thinking. He decides to take the guard's advice and wait a while before entering the building. They go to a hiding place nearby to wait.

At the armoury, there is one very bored guard on duty. After checking a computer bank, he sits down to rest, a yawn escaping his lips. A noise brings him to his feet, but it is too late. Tor and Sita descend upon him and knock him out. He has not even had a chance to draw his gun.

Vicki joins them and she takes a quick look around. After a moment, she's ready to begin. Sita breaks the light beams which begin the computerised questioning and detect the truth. The first question is "what is your rank?" to which he answers truthfully: he has none. The computer shuts off. Not only does the answer have to be truthful, it also has to be correct.

Vicki decides she must hear all the questions and so has Sita break the light beams again, but she instructs him to keep silent and let the questions run. They are typically bureaucratic - name, rank, requisition number, purpose of weapon, password, etc. Tor despairs as he hears them, knowing they could never fake an acceptable requisition number, let along any of the other information. But Vicki is not willing to give up that easily. She opens the machine and peers into its circuitry.

In his office, Lobos paces. He is anxious for an end to this standoff and calls to a guard unit to see if the gas has worked. He learns that the aliens are still in the museum, but he is certain the gas will soon drive them out. All guards must stay on alert.

Barbara and Dako move slowly down a corridor, coughing all along. They are moving much more slowly now and must support themselves against the wall. Barbara pauses to shout encouragement to her companion, but it is too late. Dako stumbles and falls to the floor unconscious. Barbara discards her handkerchief and goes to help him, but he is out cold and she too succumbs to the gas, collapsing unconscious to the floor.

At the armoury, Tor watches nervously as Vicki works, very sceptical that she will succeed. Vicki finishes her rewiring, but Tor is confused. The door is still closed. Vicki tells him crossly they still have to answer questions to get in, and they must answer truthfully. But she is excited as he rushes to break the light beam. This time there are only two questions, for which only the truth is required, not the correct answer. When she answers that the arms are needed for the purpose of rebellion, the armoury door slides open. She's done it!

Sita is first inside. He finds a large stash of weapons, more than enough to arm all the Xerons. Tor grabs a handful and Sita does the same. They will pass them on to the different resistance groups and return for more. Vicki wonders as they plan whether she has done enough to change the future.

In his office, Lobos works on paperwork when there is a knock at his door. Ian and the guard enter, Ian hiding his weapon at first. Lobos is pleased to have another of the troublemaking aliens under arrest, but Ian produces his gun and Lobos' smile fades. Lobos assures him he will gain nothing by killing him, but Ian thinks he might do it just for the sheer enjoyment of it. He asks to be taken to the Doctor.

Lobos' smile returns, certain Ian's efforts have been futile. He tells Ian that the Doctor has passed into the second stage of preparation, a point at which the freezing process is irreversible. Ian refuses to listen and orders Lobos and the guard to take him to the preparation room. That they do, moving far too slowly for Ian's liking.

Lobos' smugness returns when he sees the look on Ian's face. It is clear that he is shaken by the Doctor's waxy appearance. Lobos tells Ian that the Doctor has completed the second stage of processing and is "as good as dead". Ian's anger bursts forth and he brandishes his gun at Lobos, ordering him to reverse the process and revive the Doctor. Lobos says it has never been attempted before and is impossible, but the threat in Ian's voice is very clear: do it or die in the attempt. Ian disarms the governor as he moves toward the instruments, holding both guns on him and the guard.

Lobos begins deactivating some controls, but the machinery hum continues. Ian worries that it's taking too long, but Lobos tells him there's no way to know how long it will take. Perhaps, he says with a smirk, the Doctor will not recover at all.

In the Xeron HQ, Sita hands out weapons to a line of young men and boys - all that remains of the Xeron population on their home planet. Tor tells them to hurry to the Morok barracks to join others already on their way. They must prevent the garrison from mobilising in force or else their revolution will fail.

Vicki asks if she is to be included in the attack, but when Tor says he is counting on her, she announces she is not going. She plans instead to go to the museum to try and rescue her friends before it's too late. Tor refuses to allow it, not only for her safety but to safeguard the revolt as well. Even the gun she carries will give them away. Vicki solemnly gives the gun back, still intent on going. She gives an impassioned speech about what she must do, but avoids spelling out why. When she turns to go, Tor relents. He not only gives her the gun back, but also sends Sita with her. He promises to find them later once they have successfully secured the barracks.

Meanwhile, unaware of all that has happened, a group of guards returns to the TARDIS with cutting equipment. It is strange to them that no one is about but they carry on with their orders, trying to open the doors of the craft. They are stopped when the Guard Commander arrives. He notes angrily that the relief guard he assigned is not here. Leaving one guard on duty, he takes the other two with him, heading off to find out what is happening.

Inside the museum, not far from the entrance, zaphra gas still fills the air. Barbara regains consciousness, coughing violently. She struggles to her feet and wakes Dako. He has been hit much harder by the gas and can now barely walk. Barbara stands him up and supports him, covering his mouth and nose with a handkerchief as they move toward the exit.

Ian watches nervously as Lobos continues his work. He knows he really isn't certain what should be happening. He is relieved when Lobos announces that the Doctor's temperature is returning to normal. Lobos seems pleased with his own prowess in doing what has never been done before. Ian asks if he can't speed things but, but Lobos - a meticulous scientist - tells him the deep freeze process cannot be reversed quickly. Ian knows he's lucky it's even been reversed at all. But very shortly, the machine hum in the room winds down and stops and Lobos announces that the Doctor's normal temperature has been achieved. He should wake momentarily.

The Doctor's mouth opens and he moans. Ian goes to help him, but keeps Lobos at bay at the same time. It really seems as if the governor's scientific curiosity is overriding his anger at Ian. He is amazed at the success of the reversal. Ian helps the Doctor out of the cubicle and to a bench to sit down. He is recovering, but says his rheumatism is acting up due to the cold. He has never been quite so cold before. The two discuss this, Ian's main concern being the Doctor's safety. But they take their attention from the hostages for a moment and Lobos returns to command mode. He orders the guard to rush Ian and disarm him. Unfortunately, the hapless guard is too slow and Ian has them both in his sights again.

The Doctor chides Lobos for the sorry state of his guards but thanks him at least for reversing the freezing process... even if he had to do it at gunpoint! The Doctor explains that he was conscious throughout the time he was frozen - that is how he survived. While his body was being frozen, he kept his mind active by challenging himself with questions. Lobos disputes this, saying the Doctor's mind could easily have been affected by the temperatures. Angered by this and by the attempted freezing, the Doctor's temper flares. He says Lobos should count himself lucky indeed that his own conscience won't allow him to put Lobos through the freezing process, for that is what he would dearly like to do right now!

Ian tells the Doctor what has occurred since he's been frozen and that he thinks they should try and find Barbara and Vicki. But the Doctor is concerned, still worried that they are following the path that will lead them to becoming exhibits. While they talk, their voices drift back through the governor's office and into the hallway. They are heard by a group of passing guards who come to investigate. They see their leader being held at gunpoint and move in silently. Meanwhile, the Doctor and Ian continue their debate. Ian thinks they've changed the future by getting the Doctor out of the freezer, but the Doctor is sure Lobos would gladly put him back in again - along with the others. When the guards rush in and knock Ian out, Lobos is happy to confirm this. The Doctor is held at gunpoint again.

The guard on the TARDIS stands near the exit of the museum. He hears noise from inside. It is coughing. Inside, Barbara and Dako are nearly at the main doors. Dako worries that there will be guards, but Barbara knows they must get outside if they are to have any chance of survival, no matter what. Outside, the guard draws his gun and waits.

In the Governor's office, a hearing is taking place with Ian's poor victim of a guard as the subject. The Guard Commander relates his meeting with the guard. He explains the lie the guard told and the guard protests that he was forced to do it and to bring Ian here. Lobos is unimpressed, noting that Ian disarmed him to get a weapon in the first place. He orders the guard put under close arrest.

Lobos receives a message from the guard on the museum entrance. He is happy to hear that the zaphra gas has finally driven the aliens from hiding. Soon this "little diversion" will be over. Lobos is concerned though when he cannot raise the barracks, but chalks it up to a faulty connection. He sends the commander, along with the guard, to the museum entrance to help. It looks like the disgraced guard will have a second chance.

As they go, Lobos returns to the preparation room, where Ian and the Doctor are prisoners. Smugly, he tells the Doctor that the others in their party are about to be captured. Soon, they will all be together again... forever.

Barbara and Dako stumbled gratefully out into the fresh air, but they are quickly made prisoners. The lone guard - whose reinforcements have not yet arrived - places them against the wall. This guard at least knows how to do his job. He keeps them from talking and waits for some assistance. What he gets instead is Sita, who rushes him and fires before the guard knows what hit him. Vicki greets Barbara warmly.

Dako is dumbfounded by Sita's gun and newfound confidence. Much has clearly changed since last Dako saw him. Sita explains the armoury and Tor's attack on the barracks. The revolution has at last begun.

Barbara and Vicki try to figure out where Ian is. It seems unlikely he's still in the museum and Barbara speculates that he must have been captured. He and the Doctor are probably together. Vicki is still optimistic. She thinks she has solved the problem of their future: once the revolution succeeds, the Xerons have vowed to destroy the museum forever. That should be enough to safeguard their own future.

Sita tells the women that he and Dako will head for the barracks. Barbara thinks they should go too, but Vicki wishes to rescue Ian and the Doctor. When she learns they are likely in Lobos' office, though, she changes her mind.

However, the Commander arrives and shoots down Sita. The guard knocks out Dako and takes Vicki and Barbara prisoner. The Commander disarms Vicki and demands to know where she got the gun. Vicki says she can't remember. But the Commander thinks he knows the answer, confirming with the guard that no weapons have recently been lost to the Xerons. He takes Vicki and Barbara to the Governor's office to answer his questions truthfully.

Some time later, Lobos has examined the gun Vicki was carrying and is certain it came from the armoury. He is unable to raise anyone there and becomes even more concerned. The Commander has already sent a guard to investigate. Lobos refuses to speculate on how the girl came to possess the gun, insisting on gathering facts. One thing he does know - all four of the aliens will become museum specimens very soon.

This thought is foremost in the minds of the Doctor, Barbara, Ian and Vicki as well. They are all together again, but locked up in the preparation room. Ian vainly tries the door, but it won't budge. The Doctor tries to calm the young man down, but only succeeds in riling him more. Desperate to keep himself and his friends from their fate, Ian attacks the freezing equipment and smashes one of the control boxes. The Doctor is certain that it can be repaired or replaced easily enough, but admits - along with Barbara - that he wanted to do the same thing.

Vicki is certain they must have changed the future by now, but Barbara fails to see how that could be. They were all four separated and yet all their individual choices and paths led here. It seems their grim future is assured. Ian and the Doctor join in the regrets, but Vicki reminds her friends that they are not frozen yet. Ian is hard-pressed to figure out what they can possibly do where they are, and the Doctor points out that they have all had contact with people here on this planet and may have even influenced them. Their future could be changed for them. Vicki agrees, certain her "revolution" will be their salvation.

And it seems as if the revolution is going well. Two guards race toward the museum entrance, looking for any escape from their pursuers - a group of armed Xerons. They do not make it and are gunned down just outside, their bodies joining those of the two Xerons already there. A third guard is also killed when he tries to attack the young men. A fourth makes it inside and nearly manages to draw his gun before being killed.

Tor takes a moment to check on the two Xerons outside the museum. He finds that Dako is alive, only having been knocked out by the guards. He awakes and tells Tor what happened, including Vicki's capture. Tor takes two men with him and races for the Governor's office.

The guard sent to the armoury reports to Lobos that all the weapons have gone and that the barracks have also been attacked. Lobos listens helplessly as the guard himself is attacked and the connection goes dead. The Xeron revolution - which Lobos has always denied was possible - is painfully real to him now. It is already nearly over and has occurred entirely without his knowledge. Morok rule over this planet is finished and he knows it. Lobos begins gathering sensitive documents and packing them up. There is still a ship standing by for launching and he intends to use it to escape with his life. But first, he and the Commander plan to rid themselves of the four troublesome aliens.

They wrench open the preparation room door, their faces set and their intentions clear. The Commander raises his gun. At that moment, Tor and the others burst into the office, firing immediately. Lobos and the Commander are killed and the revolution is over as quickly as it began. Vicki runs to Tor, happy he has been victorious. The Doctor expresses what they all feel: the future doesn't look so bleak after all.

Some time later, Tor's promise to dismantle the museum is already becoming a reality. Ian, Barbara, and Vicki watch as Tor directs his men in removing and discarding all the exhibits from inside. Ian knows they are doing it as much for themselves as for him and his friends. It must be nice to get their own planet back after so long.

The Doctor emerges from the TARDIS to clutching a small metal pin, explaining that he's fixed the problem that caused their "dimensional troubles". He likens it to the occasional time delay that affects electric lights, between activating the switch and seeing light. Until the small metal pin got unstuck and clicked into place, they had not properly "arrived". Ian is happy for the explanation, but not sure he is any wiser for it. He agrees to take the piece inside the ship at the Doctor's request.

The Doctor joins Vicki and Tor as Tor is explaining why all the Morok exhibits have to be destroyed. Despite their potential uses, they are not of Xeros and so will be destroyed. The Doctor appreciates the sentiment but tells Tor not to lose sight of science altogether - it can come in very handy.

Ian comes back out of the ship, inquiring about an "extraordinary contraption" now resident inside. It is, the Doctor says, a time/space visualiser. He saw it in the museum and Tor gave it to him as a souvenir. Ian is concerned as it's so big, but the Doctor takes this as a suggestion that he cannot bring whatever he likes into his own ship and gets very cross. Barbara deflects the argument by appealing to the Doctor's scientific curiosity. He tells her he thinks he can get the visualiser working again, but he won't tell Ian what it does. He must wait and see.

The Doctor is now in a hurry to be off. He accepts Tor's thanks and bids him farewell. Vicki, too, says a fond goodbye and then joins the others in the TARDIS. Tor watches as the ship dematerialises.