A group of saucer-shaped spaceships fly through space in formation. Shortly, one peels off and lands on a rocky, barren island on a nearby planet. Its occupants emerge - two very tall male humanoids identically dressed in dark, high-collared clothing. One is clearly in command - Navigator Rago. The other is a trainee Navigator - Probationer Toba. He is a hothead who speaks his mind, caring little for the distinctions of rank. The two are mismatched and well aware of it.

Toba reports that all the local radiation on the island has been absorbed by the ship and transferred to their power reserves. However, they still need more. That is why they left formation to come here: to find fuel for themselves and their fleet. Toba thinks this was a poor decision as the planet is unexplored and appears to contain little of usable fuel stocks. Rago chafes at the criticism of his orders. A little work will provide them with fuel, work that is aided by the thin planetary crust here and the primitive life forms available for slave labour. Toba worries that the natives might be hostile - in fact he seems to hope that they are, as he will take great pleasure in destroying them. Rago reminds him they need the aliens alive for a work force and orders him to commence the initial survey. Drilling sites are to be mapped by creatures called Quarks.

In the misty sea nearby, a bullet-shaped seacraft cruises slowly toward the island. It is piloted by a cocky young man named Cully and carries three passengers: Etnin, Tolata, and Wahed. They are very unlikely adventurers, appearing to come from an indolent upper class used to power and privilege. They complain of the slowness of travel by sea, although they admit it is more exciting that way. Cully reminds them that this is an unauthorised trip to the forbidden place, known to all as the Island of Death.

As they approach, Cully plays it up, always the salesman, reminding them that the place has been abandoned for over 170 years due to the deadly radiation. His passengers are underwhelmed as they know that students visit the permanent survey unit every week to study the place. Wahed particularly is unimpressed, implying that it's not even the Island of Death out there. Because of the radiation, they can't even go out to prove where they are.

Tolata notices that they are approaching landfall rapidly and that they have heard nothing from the radiation warning system. Cully realises too late that his early warning has failed them and that they are going to crash. The seacraft beaches itself violently, tossing its occupants to the floor. They are all unharmed but the craft is wedged tight against the rocks. They are stuck. Cully begins to worry about being stranded and dying here of radiation but his sceptical passengers are more practical. Wahed goes to check the radiation readings as a precaution. They register zero and all three adventurers believe they have been conned by Cully.

Etnin and Wahed open the doors and go outside. Cully follows, genuinely confused by all of this. He is fairly certain this is the Island of Death. One thing he does know for sure - his passengers haven't paid him yet! He follows them. Outside, Tolata joins in the chiding, insisting that he never intended to take them to the Island of Death. He was just having them on. Etnin returns from a peek over the hill. He has seen people moving about without protective suits. They've also got a type of robot he's never seen before. Clearly this is not the Island of Death.

Etnin, Tolata, and Wahed move off to flag down the people, hoping they can hitch a lift back to the mainland. Incredulous, Cully has no choice but to follow them.

On the other side of the hill is the spaceship of Dominators Rago and Toba. Outside it, Toba gives orders to unseen robots to set up drilling equipment. He is interrupted by the sight of 3 people running toward him. Natives of this planet. Without hesitation, Toba orders his robots, the Quarks, to destroy the creatures. Still on the hilltop, Cully sees what is happening and shouts a warning, but it comes too late. The Quarks destroy Etnin, Wahed, and Tolata. They appear to melt before Cully's horrified eyes.

Toba is almost gleeful at his success...until Rago takes him to task for the unnecessary waste of potential slaves.

Stunned, Cully wanders off. He does not notice as the TARDIS materialises in a spot he has just passed.

The Doctor and Jamie emerge, along with their new friend Zoe. The Doctor is tired from all the exertion of projecting mental images of Daleks for Zoe and he wishes for a nice holiday. Looking around, he recognises the planet. He has been here before. It is Dulkis, a perfectly lovely and peaceful place just right for resting. There will be no Cybermen or Daleks to worry Zoe and in fact there is very little to do. He rummages in the TARDIS and produces a butterfly net, a beach ball, and a deck chair, all the while extolling the virtues of the kind, gentle, advanced Dulcians. Jamie is dubious but continues blowing up the beach ball as instructed.

Not far away, Probationer Toba continues his work. However, he has come across Cully's seacraft aground on the beach. He wastes no time in having the Quarks destroy it. Surely Rago can't object to that. Unbeknownst to him, Cully has witnessed the destruction. He is well and truly stranded here now. He throws himself to the ground and plays dead, hoping the murderous creatures will leave him be.

The Doctor, Jamie, and Zoe have heard the explosion and gone off to investigate. They find what appears to be the remains of a bombed-out building just standing in the open. But the damage was not caused by the blast they just heard. It occurred some time ago. Zoe thinks it looks like atomic blast damage. The Doctor is confused, unable to reconcile these images of destruction with the peaceful Dulcians he remembers. Moving further inside, they find more damage, but also more structure. The room they're in looks like a museum diorama, including exhibits of weapons. The Doctor must stop Jamie playing with a laser gun which he recognises as very old. This must be some kind of war museum.

Zoe spots a horrible tableau in the room. Two seated figures frozen in death - death from a nuclear blast. Cautiously, the Doctor and Jamie investigate. They are only dummies, made up to look like atomic blast victims. They are relieved but questions remain. This is clearly meant to look like an atomic test site and Zoe worries there might be radiation about through which they've all been walking unprotected. As they all turn to go back to the TARDIS, they find 3 people observing them. All three wear radiation suits.

High on a hill overlooking the island is the research station Cully spoke of earlier, a permanent site on the island from which students can observe and learn about the effect of the radiation. The Doctor's rescuers are a teacher, Educator Balan, and his two young students, Kando and Teel. Balan is concerned for the safety of the strangers due to their exposure to the radiation which bathes the Island of Death. They have been placed in decontamination and the two students monitor their exposure. To Balan's astonishment, the meters read zero. The strangers are showing no signs of radiation despite their lack of protective suits. Balan decides to let them out to get an explanation.

The Doctor testily tells Balan that they are all quite safe - he has checked and there is no radiation outside. Balan tells him that the students have just arrived and have not yet taken their readings. At the Doctor's urging, they do so now.

Balan confirms for Zoe that this is an atom test island but that it dates back before Dulkis became a pacifistic society. Balan cannot fathom these questions until he learns that the Doctor, Jamie, and Zoe are from another planet. He takes this unique occurrence in stride, continuing - with Kando's help - his explanations.

There was only ever one atomic blast on Dulkis - 172 years ago. It was a result of research into atomic power, but the destructive capabilities were developed as well. After the one test explosion, all research into nuclear power was stopped and the island maintained as a museum and as a warning for future generations. All weapons of every type have since been banned on the planet. They are a peaceful, prosperous, advanced, introspective society.

This information seems to solve the mystery of this island, but one question remains: where has all the radiation suddenly gone?

At the Dominator spaceship, Toba is learning that once again Rago is displeased with his actions. The destruction of the seacraft was unnecessary and harmful. Toba's job here is to investigate and assess objects and creatures for their potential threat...and to obey Rago. He did neither of these things, preferring to destroy first. Assessment cannot be made of that which has been destroyed. Wit this admonition, Rago returns to task.

He wonders why this island showed the only signs of radioactivity on the planet, but that is a minor concern. The drilling programme is all important as that will lead them to the fuel they need to leave this place. Toba reports that all drilling sites have been marked. Rago wishes to inspect them.

Elsewhere, Cully still wanders the island. He has come upon the TARDIS and examines its strange shape. Immediately in front of it, pressed into the dirt, is a strange mark. This is not a natural phenomenon on this planet, nor is it familiar to him. But he is forced to break off his investigation when he hears someone approaching. He hides behind the TARDIS as the two tall, black-clad creatures approach.

Rago is pleased at this choice of a drilling site but wonders about the blue box near it. Toba of course wishes to destroy it but Rago holds him back. It would be a waste of time as the primitive-looking thing obviously poses no threat to the drilling.

Over by the atomic museum, another drill site is marked. Teel, in full protective gear, investigates. He is surprised to see Cully, an old acquaintance, wander in. He, like the strangers, has no protective suit. Cully seems a bit shell-shocked but is very glad to see another Dulcian at last. He urges Tell to take him to the research station.

As they go, Rago and Toba arrive to investigate the drill site. Rago, however, is more interested in the museum. He is dismayed to learn that Toba has dismissed the structure as primitive and of no importance. From it, Rago is able to deduce that the island was a test site, hence the localised radiation. From it he has also determined a potential threat. Toba cannot see this, dismissing the weapons on display as primitive and of no danger to them. They are very old, yet one even works when he tests it. Rago impatiently explains that these are old weapons. If they are here now - on display - then presumably other more powerful weapons have since been developed. Toba erred gravely in dismissing the people here as harmless. By destroying the natives as he did, he robbed the Dominators of vital information. Toba is chastened by this enlightened analysis.

Rago says they must find more of the native creatures to question and examine.

In the research station, Kando serves refreshments as theories are bandied about as to the disappearance of the radiation. Balan thinks the TARDIS the Doctor spoke of might have absorbed it, but he is grasping at straws. Aliens have never visited Dulkis before - as far as anyone knows - and while the fact-based Dulcians easily accept that the Doctor and his friends are aliens, they also entertain wild theories to explain other facts as well.

The conversation is interrupted by the return of Teel. He has found no radiation outside, but he has found something else: Cully. The anxious man brushes off the niceties and demands to be returned to the capital immediately. He has seen aliens and robots out there and he seems genuinely afraid.

However, limited by facts, Balan cannot accept more aliens he hasn't seen and combines Cully's and the Doctor's stories. He refuses in the end to believe that the Doctor and his friends are aliens, chalking it up to more of Cully's tricks. His reputation as a joker far precedes him on this planet. The son of the Director of the ruling council is well known as a con artist. However, the Doctor believes him, especially when he talks about the blue wooden box he's seen and that the aliens spoke of possibly destroying it. Alarmed, the Doctor and Jamie race off to investigate. Zoe decides to stay behind.

Balan ignores all this hoopla, certain that the explanation for this whole business lies in another of Cully's scams.

Back at their ship, Rago is pleased that the drilling sites are ready He orders the Quark robots to begin drilling on the outer bore holes immediately and Toba to report their progress to the Fleet Leader.

Balan continues to deny Cully's claims of aliens and refuses to take any action until he has spoken to Director Senex, Cully's father. Cully of course knows the response already - do nothing. That is typical of Dulcian society these days. Status quo. Clearly he disapproves. However, Tell cannot reach the capital due to interference over the communication lines. Cully is angered at this inaction but is glad at least that the Doctor showed some interest in his story.

Jamie and the Doctor have finished inspecting the TARDIS and have found it unharmed. The Doctor investigates the impression in the dirt and calls it a survey mark of some kind. He also sees a series of blockish footprints in the dirt, leading away. They follow. The prints lead them to the circular silver spaceship Cully described. It is clearly not from this planet.

They approach more closely, going straight up to the entrance of the ship, a cylindrical entryway which extends from its belly. No one is about. Jamie is starting to get worried but the Doctor actually turns to venture in through the open hatchway. Jamie stops him with an urgent tug on his coat.

The Doctor turns to see Rago atop a hill nearby, two robots at his side. They are very small and boxlike, their heads round with five pointed appendages coming off at all angles. They appear to share Rago's interest in destruction.

Toba for once obeys Rago's orders and calls off the overeager Quarks. The Doctor and Jamie are taken prisoner.

They are brought to the Dominators' ship and are made to stand before Rago and Toba. The Dominators stand on the control dais to magnify their height and power. The Doctor seems a bit in awe of them and obeys when told to stand near one wall. Jamie refuses to obey until a Quark approaches. For his disobedience, both prisoners are fused to the wall with a bimolecular force field and cannot move.

Rago tells them that alien races are occasionally "useful" and he intends to probe their physiological make up to see if they will be. The wall on which Jamie is fused tilts outward to become a table and a harsh light appears over him. Rago performs a molecular scan with the help of the Quarks. He determines that while Jamie's body may be marginally useful for physical labour, his brittle skeletal structure and single heart make him less suitable. While his brain shows signs of recent rapid learning, it is primitive.

To his astonishment, the Doctor is spared this procedure as Rago assumes they will be the same. A critical mistake made in the interest of conserving the Quarks' precious power. A second mistake is in assuming that the two prisoners are native Dulcians, a belief that the Doctor will not refute. Toba advocates killing these inferior creatures but Rago wishes them to be spared for further tests and to conserve power. Toba reluctantly accepts the command.

The next test is a reaction test. This time, the Doctor will be the subject.

At the survey unit, Educator Balan has managed to get through to the capital on video, although the reception is poor. Cully has spoken to his father, Director Senex, but he seems sceptical of the story. He will listen no more to the garbled information and orders Cully and the strangers to the capital and switches off the link.

Cully is angry and the cool disbelief and lack of concern that seems to be typical of the complacent Dulcians these days, but he knows he must follow the order. The fuel cells on Balan's travel capsule are charging now. Zoe is curious about the travel capsule and the trip to the capital, proof positive that she's not a Dulcian. No one here is curious!

Shortly, the cells are charged and Cully and Zoe set off in the two-person flying pod. The Doctor and Jamie will be sent along when they return. Balan himself sets the controls for the capital to make certain Cully actually gets where he is supposed to go.

The flight is smooth and uneventful. It should be a very short ride.

The Doctor and Jamie must cool their heels - still fused to the wall - while the Dominators debate the merits of keeping the prisoners around. The Doctor strains to overhear them but only discerns talk of an intelligence test. Problem is, he can't tell whether it would benefit them more if they are found clever or stupid. Which attribute would help keep the Doctor and Jamie alive?

Before Zoe knows it, the travel capsule has arrived in the capital, the heart of Dulcian society.

Nearby, in the chamber of the ruling council, the planet's leaders conclude a long-standing debate regarding land use. They all appear to be in agreement...and then fall into fractious debate again regarding Director Senex's stand on the matter. And he isn't even present! Clearly this is a society prone to protracted and detailed discussion about anything and everything. Into the midst of this highly-minded order bursts Cully - literally and figuratively - disrupting the serenity with a loud voice and insistent manner. Zoe follows quietly.

The councillors are outraged at Cully's brazenness and mock his story that Zoe and her friends are aliens. They are well aware of Cully's history as a liar and conman, and even the few councillors who actually support the idea of life on other planets think it unlikely that a single space vehicle has landed on the Island of Death, let alone two. Director Senex enters and silences the loud debate and dismisses the councillors. He wishes to speak to his son alone. The councillors exit, continuing their debate.

But, alone with Cully and Zoe, Senex chooses to question Zoe first. He of course believes her to be a Dulcian and chastises her for going to the island and exposing herself to the extreme danger there. He also chastises Cully for taking her there. Senex and the council have long known of Cully's "secret" adventure tours, but this is by far the most serious breach of safety and common sense. It is an embarrassment to them all.

Zoe tries again to explain how she came to the island with Jamie and the Doctor in the TARDIS but this stretches Senex's credulity to the breaking point. Angered, Cully blurts out the entire situation: a spaceship, three Dulcians killed, the absence of radioactivity, and robots. Senex seems willing to consider this story - it's almost too fantastic to be a lie - but when Zoe cannot confirm it all, Cully's word cannot be taken seriously.

The Doctor has been watching as the intelligence test is set up - a simple shape-matching puzzle contained in a clear Perspex box. He is worried as it looks a bit too simple to be useful. However, all that worry might be for nothing as the Doctor and Jamie discover that they are no longer fused to the wall. They try to sidle out, only to be stopped by a Quark. The attempted escape is of no matter to Toba as the test is now ready.

The Doctor is seated before the puzzle box and a Quark attaches its force units to the box. The Doctor is given an electric shock which he is told will be repeated at intervals until the puzzle is reassembled. But the Doctor does not solve the puzzle and must endure two more shocks before Toba stops the test in anger. Jamie helps his friend up as he recovers. It seems the Doctor has decided that feigning stupidity is their best choice to stay alive. He deliberately failed the test and urges Jamie to do so as well at the next test.

Toba has the Doctor and Jamie sit on the control dais whist the Quarks attach force units on each side. He orders the prisoners to find a way off the dais. The obvious way - stepping down - leads to more electric shocks. Toba stops the test when the two men show no signs of finding a safe way off.

Rago returns to find his subordinate angered at the uselessness of these feeble-minded creatures. But Rago stays him, thinking there is more to this than is readily apparent. He reminds Toba of the weapons they saw in the museum. They could hardly have been devised by idiots like these. There is clearly more to this and he will find it out.

He gives a message to one of the Quarks to be transmitted to Fleet Leader: material readily accessible, fleet to proceed to Dulkis to refuel, investigation into potential slave labour continuing. Then he calls the Doctor and Jamie to come with him. However, they cannot leave the dais until Rago tells them to jump over the electrified area. The Doctor feigns total ignorance of electricity but Rago is unconvinced. He sees intelligence in the Doctor's eyes and wishes to give a final, conclusive test.

Back at the survey unit, Kando worries over the strangers' protracted absence. Meanwhile, Tell has been preparing a graph of their radiation findings. After 172 years of slow steady decline, all of the radiation has suddenly disappeared from the island. With typically simple Dulcian logic, Balan concludes that the effects of nuclear radiation last for only 172 years and then go away. He thinks it pointless to ascertain why this is so, despite the curiosity of his students. Clearly Cully's story of robots and aliens has gotten to these young people.

Rago has taken the prisoners to the war museum and has placed a laser weapon into the Doctor's hands. He then badgers the Doctor into explaining and/or demonstrating the weapon created by the Dulcian people. Perhaps he thinks the Doctor will reveal himself by trying to use the weapon on the Dominators themselves, but whatever the plan, the Doctor thwarts it by playing dumb. Rago then hands the weapon to Jamie, who also plays dumb, but is careless with the deadly laser, pointing it at the Doctor. He is forced to knock it aside and he tells Rago that guns were outlawed hundreds of years ago on Dulkis. The people no longer understand them.

To test this story, Rago points the gun at the Doctor and fires it. The aim is deliberately off and a hole is burned in the wall beside the Doctor. But it has the intended effect at the Doctor starts talking. He makes up a story about "the clever ones", a higher form of Dulcian responsible for the weapons, and their banning. There are few of them left now and the two races do not get along. Amazingly, Rago accepts this story as it fits the available facts. The primitives are harmless and may be used as a labour force should the need arise.

Toba of course wishes to destroy these two but Rago reminds him of their precious energy reserves. The prisoners are let go and warned to stay away from the Dominators and the Quarks. The Doctor and Jamie breathe a sigh of relief as the bloodthirsty Dominators leave the museum.

The Doctor turns his mind to the question of what the creatures want here. It sounds as if they are looking for mineral deposits or something similar, but the need for a labour force perplexes him. Once the Quarks are out of sight, they decide to return to the survey unit as Zoe will likely be worried about them.

Cully and Zoe have been left to cool their heels in the council chamber while Senex reflects on what they have reported. However, Cully is certain the outcome will be disbelief and so decides to go back to the island and get proof of the story. Zoe agrees to go with him and they start to head out through a secret back entrance. They must then steal a travel capsule, but Cully is concerned that Zoe will attract too much attention in her decidedly non-Dulcian clothing. They'll have to get her properly outfitted using the clothing dispenser in Senex's rooms.

Back at the survey unit, Balan quickly bundles the Doctor and Jamie into a travel capsule and sends them off to the capital. He has only enough time to tell them Cully and Zoe are already there. And then the capsule is sealed and gone.

However, the Doctor's information about the Dominators and Quarks has resonated with Teel and Kando. They both are inclined to believe him and approach Balan with the idea of going out and looking for themselves. Seeing that he will get no more work from his students until they are satisfied, the pragmatic Balan agrees to go out with them in search of the aliens and their killer robots.

Zoe is soon kitted out in the short, sheer Dulcian garments and Cully approves. She herself feels that they aren't "very efficient" garments. But at least it will help them procure a travel capsule. They head off to the terminal.

On the Dominators' ship, preparations continue for the drilling that is to take place to obtain fuel. However, a Quark reports three strangers approaching. Toba wishes to destroy them, and a frustrated Rago must once again hold him back.

Outside, Balan, Kando, and Teel are awestruck at the sight of the large alien spacecraft. The two young people are excited and wish to go inside. Balan, still wishing to confirm every aspect of Cully's story, agrees. They are observed on a monitor inside as they approach.

They enter the control room and look about them, scarcely believing the fantastic technology within. The place seems empty but that is only temporary. Rago, Toba, and the Quarks appear from hiding, the robots ready to kill at the first order. The simple Dulcians are at first pleased to discover the proof of Cully's story firsthand, but then fear sets in as they remember all that he told them of the aliens and their robots. Balan is force-bonded to the control dais whilst Tell is put on the examination table like Jamie before.

Rago conducts the exam and quickly discovers that these creatures are different that the others. They have higher brains and two hearts. They must be "the clever ones" of which the Doctor spoke, but Rago pronounces them harmless. Toba is finally getting the picture as he realises these creatures can be used as a labour force, but they'll need more. Rago proposes a further search of the island.

Cully and Zoe enjoy the ride back to the island. However, it occurs to Cully that the Doctor and Jamie are probably on their way to the capital right now. They're probably passing each other on the journey. At any rate, they can always turn round again...as long as all is well at the survey unit.

Meanwhile, the Dominators search the island for more Dulcians, splitting up to cover more ground. Toba finds the survey unit.

Cully and Zoe head for a landing at the survey unit, unaware that Toba and two Quarks are inside. Luckily, the robots complete the downloading of all computer information and leave the building before the capsule arrives. Once outside, Toba has the Quarks quickly recharge.

The survey unit is eerily quiet and completely deserted when Cully and Zoe emerge from the capsule. They can find no reason for this, but it doesn't look good.

Toba orders complete destruction of the survey unit and whoever is inside. But before the Quarks can comply, Rago arrives and countermands the order. He is, as before, most displeased.

Inside, Zoe and Cully are unharmed, but they fear more attacks. Cully is certain it is the robots attacking but Zoe doesn't care for speculation. She just wants to get out of here. They try again to open the door.

Toba tries to offer an explanation. Rago refuses to listen, chastising his subordinate for precipitous action and wasteful destruction. Rago orders him to find any survivors and return them to the ship... alive.

Zoe wonders why they can't use the travel capsule to escape but Cully thinks it too dangerous. Even if they could get past the robots, he couldn't steer it with the controls damaged at this end. He decides to have another go at the door. This time it opens easily, because he has help. Outside, a Quark is waiting for them.

Councillor Bovem escorts the Doctor to the empty council chamber. There they must wait for Director Senex. They learn from Bovem that Zoe is not here but he will reveal nothing more. He goes off to fetch Senex, leaving the Doctor and Jamie perplexed.

In the Dominators' ship, Balan and Kando worry about what will happen to them and why these creatures would want to hurt them. Toba returns with his prisoners but Rago is way ahead of him. He has already scanned the cerebral cortex of Teel and found it sufficient for slave labour. However, his muscular and skeletal systems are somewhat weak. Their use as slaves is questionable.

To make the decision, Rago decides to test the prisoners. He will put them to work on the drilling sites to see how long they'll survive. That will determine whether or not they are suitable as a species for long-term work.

Before Toba heads out, Rago passes on another order. A Quark is to be put on guard at the survey unit in case any one else arrives. He wants more prisoners to test.

Jamie and the Doctor learn from Senex of Zoe's return to the island with Cully. Jamie is angered that they were allowed to return into danger and demands to know what the Dulcians will do about all of this. Both Senex and the Doctor remind him that Dulcians are total pacifists and that there is no question of fighting Quarks. Senex and the other councillors are beginning to believe that Jamie at least must be from another planet as he clearly knows so little about Dulkis.

The Doctor tries to turn the conversation to the matter at hand. Senex reveals that they now know who went with Cully to the Island of Death initially, but he and the others refuse to believe that Etnin, Tolata, and Wahed were killed by Quarks. The Doctor's insistence on the ruthlessness of the Dominators does no good and Jamie is quickly losing patience. He is certain that while they sit here and rehash events, Zoe is in great danger.

At this moment, Zoe and Cully cool their heels outside the ship whilst waiting for work to begin. Both are bent on escape. Zoe is certain that they can put the Quarks out of action with the right sort of weapon. She remembers the laser gun on display in the museum and her spirits lift as she realises they might just stand a chance... if only they can evade the Quarks guarding them and get into the museum.

On board the ship, Balan, Kando, and Teel are released to join the work party, a Quark escorting them out. Toba is to follow but Rago holds him back. He wants to make certain his orders are clear this time. The prisoners' work rate and other data are to be observed and recorded for analysis. They are not to be harmed for any reason, including attempted escape. In fact, Toba is to take no personal action at all. Toba finds this restraint difficult to take, but grudgingly accepts the command. Whether or not he obeys is still to be seen.

Zoe learns from Kando and Teel that the Doctor and Jamie have gone to the capital. Clearly they are on their own for the time being and can expect no outside help. Toba arrives to herd them all to their first work site.

The Doctor describes to the councillors the tests to which he and Jamie were subjected and the reason for them. But the fact that they were let go unharmed in the end does little to inspire fear in the stoic Dulcians. In fact, it makes Senex disbelieve the threat entirely. He and the other councillors are uninterested in sending one of their people to the island to verify the facts. They are content to question the Doctor at more length.

The Doctor can only speculate as to the Dominators' objective on the island, although he does tell them of the drilling sites and the "material" which is readily available. Senex thinks this unlikely as there is no mineral ore there and these Dominators are welcome to take anything they can find. Even the sudden disappearance of the island's radiation seems insignificant to Senex. He concludes that there is no threat. Jamie is flabbergasted at this calm acceptance of danger, but one of the councillors sums up Dulcian philosophy: better to do nothing than to do the wrong thing. A debate on the historical use of arms ensues, driving the practical Jamie to distraction.

Senex explains that universal gentleness causes evil to die and the Dulcians will stick to that ideal. Jamie explains - shortcutting the rules of debate - that the Dominators don't know about Dulcian "gentleness". The Doctor cuts through the impasse by suggesting Senex try to contact Balan at the survey unit to see if he's gathered any more information. However, there is no answer there. The view on the monitor shows the astounded councillors a ruined building and a Quark on guard. They are taken aback by such a stark, violent image.

The Doctor and Jamie believe this proof enough of their story and are now worried about Zoe, who was headed back to the survey unit. They race to a travel capsule to return there and are soon on their way.

However, in his haste to leave, Jamie fears that the Doctor may have forgotten something vital. The capsule is heading to the survey unit, straight into the arms of the deadly Quark!

Back on the island, the prisoners are given a lecture before starting work. Toba tries to explain how if they do a good job clearing debris from the drilling site, they may just be kept alive to serve the Dominators, mighty masters of the 10 galaxies. However, Zoe and Cully continually interrupt with questions and concerns. Finally, an angry Toba silences them by reminding them that if they prove unsuitable for slave labour, they will be destroyed. Then he is off.

This makes an impression on Balan and he exhorts his students to start working immediately, clearing very heavy rocks and debris from the site near the atomic museum. He refuses to listen to Zoe as she tries to figure out some way to escape. The odds are good - five people and only two Quarks - but it will only work if they all pull together. Balan and Kando refuse to fight, preferring the security of obedience. Teel is on the fence, leaning toward resistance, but without all of them there can be no plan.

The Doctor begins dismantling the control section of the travel capsule, much to Jamie's horror. But this is the only thing for it to alter the capsule's flight path. There are no manual controls and the Doctor must delve into the tangled mass of wires he's revealed to gain any control over it. All the wires lead into the nose of the bullet-shaped capsule and the Doctor is forced to crawl up inside it. Jamie watches, growing more worried by the second, as the Doctor disappears up to his waist.

Rago transmits data on their location and investigations to Fleet Leader. So far, all is going well. A Quark arrives with an initial report on the slaves. All are showing signs of fatigue, but one is significantly less tired than the others. Strangely, it is one of the women. Rago takes this in thoughtfully and orders the work to continue. All should be forced to the point of exhaustion, with careful note taken of who collapses and when.

It is Zoe with the most strength. She is still going strong. Cully, too, seems to have some energy. The other 3 are fading fast. Cully is more worried than ever; even if they can convince the others to help in the escape, they'll soon have no energy to carry out a plan. And the odds are even better now with only one Quark on guard.

Fortunately, their first work site is the one near the atomic museum. Zoe returns to her idea of sneaking into the museum and getting hold of the laser gun, but she is interrupted when Balan suddenly cries out and collapses. He has reached the point of exhaustion. All the prisoners run to help.

The Quark orders them all to get back to work, despite Cully and Zoe's insistence that Balan can work no more. It finally understands that Balan is "broken" and orders him moved aside whilst the work continues. They comply and the Quark returns to guard duty.

However, Zoe finds herself alone and unwatched as Cully, Kando, and Teel go back to work. She seizes the opportunity and sidles to the door of the museum. Unfortunately, she is greeted by the second Quark, returning from its reporting. It forces her out and back to the work party.

With Jamie's help, the Doctor extracts himself from the capsule's nose, coming out with a small black box into which all the wires seem to terminate. With this, he hopes to steer the capsule. His initial attempt sends them wildly out of control, but he regains command quickly. Steering seems easy enough after that. The only difficult bit will be landing... in one piece.

The Dulcian ruling council is left to debate the current situation, given the facts as they are known. There seems to be some general agreement that there may be a threat in the Dominators, but talk of action spurs more debate. Bovem suggests that while the Doctor's advice and assistance are valuable, the Dulcian people can hardly entrust the salvation of their world to an alien, no matter how friendly he appears. Bovem suggests turning the matter over the Chairman of the Emergencies Committee, a man called Tensa. Senex does not doubt that Tensa has ably handled all manner of natural disasters, but wonders whether an intelligent, aggressive threat is something beyond his scope.

Tensa arrives in the council chamber, a younger man than the councillors and as close to a "man of action" as Dulkis will ever produce. He has already heard the facts of the situation on the island. While he believes the facts don't conclusively define a threat, he has already formulated three options: fight, submit, or flee. The councillors all leap from their seats in protest and Senex spells out their concerns. They cannot fight, there is nowhere to flee, and submission could mean the end of Dulkis.

So, they conclude, they can take no action. They must wait. The councillors sink wearily back into their seats.

The Doctor and Jamie arrive safely on the Island of Death. The capsule is half-buried in the sand, but it is in one piece. So are the Doctor and Jamie, who stagger sorely out of the capsule. Jamie is a bit cranky over the bumpy landing but is more than ready to head off to try and find Zoe.

As they've laboured, Cully and Zoe have been working on Teel, trying to get him at least to help them in their escape plan. Seeing Balan and Kando exhausted by the back-breaking work, he's ready to try anything. Zoe convinces him they can reach the laser gun without harm. But they also need someplace safe to hide. Teel remembers an atomic shelter supposedly built on the island during the tests but he doesn't know where it is.

Jamie and the Doctor arrive on a ridge above the atomic museum and are glad to see Zoe alive and well, along with Cully. However, Balan and Kando are lying on the ground. It doesn't look good and they must act fast to help. The Doctor and Jamie split up to descend on opposite sides of the work area.

Not knowing of the help on the way, Zoe and Cully prepare to put their plan into action. Cully pretends to collapse and is ordered to join the other "broken" specimens. Zoe continues working and the Quarks' attentions are directed at her. Cully keeps on going, beyond the work area and up into the museum. He gets in unseen and hurries to pick up the laser gun. He sights it out the small window, aiming for the Quarks.

Outside, Zoe sees that he is in position and feigns collapse as well. The Quarks approach her, noting the time of collapse. There is an agonising silence during which Cully does not fire. Zoe worries that he'll miss his chance.

Just as Cully is about to squeeze the trigger, he is stopped by a hand on his arm. To his surprise it is Jamie. The lad was afraid that Zoe would be harmed but he has managed to blow the opportunity to hit the Quarks. Cully tries again to get a clear shot at the robots but Balan and the others get in the way as they are forced to stand and march back to the ship. Then the Quarks notice the missing specimen.

Jamie is abject in his apology and suggests waiting for the Doctor to join them before doing anything else. Cully only hopes he's not too late in arriving.

The Doctor, however, has problems of his own. He has run into Toba, who was heading back to the work site. The Doctor pleads ignorance but Toba is unamused. They are shortly joined by the Quarks and their four prisoners. Toba is furious to learn that Cully has escaped and decides to take action. He sends the prisoners - including the Doctor - back to the ship under Quark guard and takes 3 Quarks with him to find Cully.

Cully and Jamie are getting concerned over the Doctor's absence and try to decide what to do. Unfortunately, Cully paces in front of the window and is spotted when Toba arrives. Toba vows revenge for the disobedience and orders a Quark to fire.

The museum's door is blown off and Jamie is knocked off his feet. Riled, Jamie takes the gun and fires it out the window. His aim is true and a Quark explodes.

Toba is stunned by this, furious that these simple-minded aliens could destroy a mighty Quark. His reaction is quick and instinctual. Destroy! Total destruction!

Toba returns to the spaceship and reports the incident. He is certain that Cully and Jamie are dead. The Doctor, Zoe, and the Dulcians are stunned and worried. Rago's reaction is somewhat different: he is livid.

Toba deliberately disobeyed his orders not to harm the creatures and he does not accept any arguments from him. There was no justification for this actions. He orders Toba to take Balan, Kando, and Teel to the central bore site and clear it for drilling. The "inferior types" - Zoe and the Doctor - will stay behind. Toba cannot believe his luck and tries to get outside as quickly as possible. At the last minute, Rago stops his subordinate and sends a Quark to oversee the slaves. Toba is to stay behind for a moment.

And then comes the dressing-down. Navigator Rago upbraids Probationer Toba for disobedience and for destroying the harmless primitives on this planet. It is bloodlust, pure and simple, that has led him to these actions. Rago very much doubts that Toba has the detachment and intelligence necessary to rise above his probationer status. Toba protests at this, pointing out that these creatures may not be as harmless as they appear. Rago accepts this possibility and determines to investigate "the clever ones" further. However, he still disapproves of Toba's miserable performance and vows to report these incidents to Fleet Leader.

Suddenly Toba turns the tables and vows to report Rago as well - for unnecessary softness that might jeopardise their mission. Rago is stunned at the threat and makes one of his own - a deadly serious one. Toba's execution for treason. A Quark comes forward on his order, force units pointed at Toba. There is a joust for control over the creature and a long moment of silence when Rago wins out. In the face of destruction, Toba submits. Rago tells him he is lucky to still be needed on this mission or he would be dead already. Toba is released to oversee work on the drilling sites. He leaves the ship in a hurry.

The Doctor and Zoe have only a moment to ponder this internal dispute before Rago turns his attention back to them. He has some questions he wants answered...

Toba orders Kando and Teel to complete work clearing the drill site next to the atomic museum whilst he takes Balan to another site. There is new debris next to the museum - the remainder of the shattered building. Kando and Tell see no sign of Cully there and fear that he's been crushed under the debris. His only hope would have been to find and enter the atomic shelter. If not, he's dead.

Unnoticed, the debris pile in the museum shifts slightly, being pushed from below. It is indeed Cully and Jamie. Beneath the rubble is the hatch that leads to the atomic shelter. Inside, Cully and Jamie are alive but trapped. There is so much debris on top of the hatch that they cannot open it. They are stuck here with little chance of being rescued. Still, Cully is glad they took the extra time to destroy the Quark before coming down here. Jamie, thinking of this, worries about repercussions on his friends and starts to attack the hatch again. No good.

As Jamie descends the ladder, breathing hard, he notices how stuffy it is inside the shelter. There is only one air vent in the little room and it now becomes clear they have a new problem. If the vent is blocked from above, they'll suffocate long before anyone finds them!

With Zoe under threat of harm, the Doctor answers Rago's questions. He tells the Dominator that Senex is Director of the ruling council, the leader of the planet, and that he is in the capital. Rago wishes to go there but realises that Toba destroyed their access to the travel capsule terminal at the survey unit. The Doctor is secretly pleased at this until Rago decides to take his own ship to the capital. Suddenly the Doctor cannot help quickly enough, telling Rago where to find a capsule on the beach and how to operate it. He even agrees to show him where it is.

While Rago prepares to leave, the Doctor steals a moment with Zoe, telling her not to worry. He explains that he gave Rago this information in order to keep the Dominator ship here on the island. He hopes to have time to investigate its power unit. If he can determine what sort of fuel that Dominators are looking for, perhaps it will help him stop them. Besides which, the capsule is too small to take them along. He and Zoe might find a way to escape and look for Jamie if Rago's gone.

Zoe agrees with all this, but before she can explain about the atomic shelter, Rago rejoins them. Zoe is released from molecular force and she joins the Doctor, Rago, and a Quark as they head off to find the travel capsule.

Meanwhile, Balan has completed the clearing of another drill site. At Toba's order, he places the strange drilling machine on the exact drilling point noted by the survey mark pressed in the dirt. The Quarks power the machine up and begin drilling, but are stopped immediately as another Quark approaches. It has been sent by Rago to fetch Toba. Clearly Rago is taking no chances with his hotheaded underling. Drilling recommences as Toba goes off to give his report.

Rago is pleased by what he sees of the travel capsule. It is primitive and the controls have been tampered with, but it is more than serviceable. He is also glad that the Doctor told him the truth. Rago believes he is at last receiving the respect he deserves.

Toba arrives and reports on the status of the drilling operation. Rago informs him of his impending trip to the capital and pays little attention to the Probationer's concerns. Toba is to command in his absence, but Rago makes it perfectly clear that he expects to find the same number of living Dulcians on his return!

Whilst they are left alone, Zoe manages to tell the Doctor of the atomic shelter and how she thinks Jamie and Cully might have survived the blast, but they can do nothing about it as Toba takes charge and leads them away.

The two men are indeed still alive and fighting harder than ever to force open the hatch on the underground shelter. With their combined efforts they at last manage to shift the rubble and force the hatch open. They hurriedly climb the ladder.

Jamie is first up, gratefully breathing in the fresh air. Cully follows. Just outside the ruined museum, they see Kando and Teel working to clear the drilling site, under the watchful eyes of some Quarks. Having already destroyed one Quark, Jamie is keen to try again, certain that the Dominators will be much less trouble without their killer robots. Cully is concerned as they no longer have a laser gun but finds Jamie's confidence contagious. The lad is ready to use everything at hand to attack the Quarks. Just as he did with the Redcoats back in Scotland. Cully is with him and they set out to find a way.

From the ridges overlooking the 5 drilling sites, Jamie and Cully find seven Quarks in all. They also spot Balan, helplessly watching as two Quarks drill. Knowing the strength and location of the enemy, Jamie is now ready to act. Cully follows along, wondering what he's up to.

On board the Dominators' ship, Zoe and the Doctor are under guard. Toba is with them until he receives a report. Drilling is progressing on the four perimeter holes. The centre drilling site is nearly cleared and will soon be ready for drilling. Toba is pleased and dashes off a report to Fleet Leader.

The Doctor is becoming more desperate to figure out what the Dominators are drilling for but he can do nothing as long as the Quarks are on guard. They need a diversion...

Outside, Jamie is unknowingly providing that diversion. Armed with several large rocks, Jamie attacks the Quarks near Balan. Drilling stops and the robots fire at Jamie but he is unharmed. He hurls more stones and one of the Quarks decides to come after him. This was part of the plan. From higher on the ridge, Cully rolls a very large boulder down the hill. It gathers great speed and bowls over the little robot, destroying it.

An alarm sounds in the ship and Toba is shocked. These primitives have somehow destroyed another Quark. Angry, he takes a Quark and goes to investigate, leaving Zoe and the Doctor alone in the ship.

They waste no time in investigating, looking for the ship's fuel source. The Doctor is buoyed by the belief that Jamie caused the destruction of the Quark. He and Cully are clearly alive...and kicking. Zoe suggests ultra sound as a power source but the Doctor discounts this. He believes it is more likely to be average electro-magnetics, but is not sure how it's produced.

Shortly, the Doctor finds the fuel cells but is surprised to find only an atomic storage unit, no generator. It is clear to him now that they use nuclear material, but only that produced externally. That explains the loss of the radioactivity on the island - the ship sucked it up and stored it for use. However, it doesn't readily explain the drilling project going on outside.

A furious Toba arrives at the site of the attack and ruthlessly questions Balan. The old man denies seeing anyone but the Quarks insist that natives of this planet attacked. Toba is certain a Dulcian force has arrived and instructs the Quarks to seek out the newcomers and to destroy them.

Back in the capital, the endless debate of the ruling council continues. Tensa continues to insist on doing nothing, somehow hoping this "emergency" will go away, and Councillor Bovem agrees. Director Senex thinks doing nothing is dangerous and wishes to take action to at least convince these Dominators that no harm is intended.

Suddenly the debate ceases when Dominator Rago bursts in. He is tall, imposing, and imperious. He wishes answers from Senex regarding the suitability of the Dulcian people for slave labour. Incredibly, Tensa and several councillors try to inform Rago of the "proper procedure" for obtaining an audience with the Director. Rago ignores the petty voices and continues. However, Tensa persists with his "protests", demanding respect for Senex.

The stunned councillors fall silent and Rago has their undivided attention. His demand for slaves seems straightforward enough but Senex still cannot understand. He says that the Dulcians would gratefully provide "assistance" to the Dominators if asked. Rago scoffs at this ingenuousness and explains in detail to make these simpletons understand. The slaves will be taken away from Dulkis and transported to the Dominators' home planet. There, their labour will replace the Quarks, who are needed at the front lines of the Dominators' ever-expanding war mission.

This at last is clear and Senex thinks he realises what danger his people face. But there is more. Those that are not selected as slaves, says Rago, will die here on Dulkis, but he refuses to say why or how. Rago turns to go, leaving his threat hanging in the air. He says he will return with specifics as to the number of slaves required, but Senex should begin gathering specimens right away. He points out Tensa's charred and crumpled body as a reminder of what will happen if he is not obeyed.

Rago storms out, leaving Senex and his councillors to ponder their fate.

Meanwhile, Toba has turned to Kando and Teel to find out who destroyed the Quark. He is furious and threatens both of their lives. When he has a Quark target Teel for death, Kando cracks and says she thinks the attacker was Cully. Toba does not believe her, certain he killed Cully in the museum, but he does remember that he hasn't seen the boy in some time. He might have survived, but he must be hiding somewhere. He gathers the two prisoners, determined to find Jamie and destroy him.

Balan has been returned to the ship and is held prisoner by Quarks along with Zoe and the Doctor. He agrees that the attackers must have been Jamie and Cully but the Doctor has other things he wishes to talk about. Specifically, the source of the original nuclear material for the Dulcians' tests 170 years ago. Unfortunately, it was in the Northern Hemisphere of the planet, far from this island.

Balan notes the thinness of the planet's crust here on the island and the Doctor is intrigued. His initial guess - radioactive magma - is disproved, but he persists. The Dominators' odd drilling pattern might yield a clue - four holes on the corners of a square and 1 hole in the centre. However, before they can speculate further, Toba bursts in. He is livid and wants information from the prisoners. Now!

When no one answers, he vows to kill them all one-by-one until they talk. Toba waits only a second before ordering the Quark to kill Balan. The old man falls to the floor in a smoking heap, dead. The Doctor is next and the Quark lines up.

Suddenly Rago bursts in, taking in the situation quickly. He halts the Quark and angrily addresses his subordinate. Toba protests that he was in a state of emergency due to the destruction of the Quark but Rago will not listen. There is no excuse to halt the drilling and to waste the Quarks' dangerously low power reserves scouring the island. Toba reports that the four perimeter bore holes are complete but Rago knows that the centre hole is not even started. He will listen to no more arguments, his voice full of menace.

Rago orders Toba to prepare rockets for the outer bore holes and to check the "seed device". Toba protests that there has not been enough time for the seed device to reach critical mass, but Rago blames that on him. If he has jeopardised the most vital part of their mission with his petty vendettas, Rago vows to leave him on this planet to die.

Luckily for Toba, the seed device - a small egg-shaped capsule - is nearly at critical mass. Toba is sent to complete the drilling and to prepare the rockets, keeping the prisoners under guard while Rago checks with Fleet Leader regarding the need for slaves.

Jamie and Cully have been rousted by the Quarks and chased all over the island. Things look bleak as they are cornered high up on a ledge with nowhere to go. Their incredible luck holds as the Quarks stop the chase abruptly and retreat. Unknown to Jamie and Cully, the robots have been recalled by their masters.

Jamie and Cully return to the atomic shelter to rest and recover. After some food, Jamie thinks he'll be ready to attack again. However, the tasteless survival rations do little for the lad's taste buds. Jamie checks the periscope and is overjoyed to see Zoe and the Doctor arriving at the drill site, just outside. Kando and Teel are there as well, although Balan is absent. There is also a Dominator and several Quarks working at something on the site. Jamie decides to try and free their friends and bring them to the shelter. He begins gathering up sheets from one of the bunks as part of his plan.

The drilling begins on the final, central bore hole while the Doctor, Zoe, Kando, and Teel cool their heels nearby. One Quark guards them. The Doctor believes he has figured out the Dominators' plan - not to take something from the ground but to put something in - but before he can explain, Jamie appears from the ruins of the museum. He approaches the Quark silently from behind and uses the sheet to bind its legs. A quick distraction from the Doctor allows Jamie to tip the robot over. Cully covers its head with another sheet and the prisoners scramble. The Quark sounds an alarm as they escape.

True to his nature, Toba ceases drilling and pulls the Quarks away from the task. He rights the distressed robot and orders all of them to search and destroy.

Rago arrives and immediately countermands the order, livid once again at Toba's disobedience. He fears that the Quarks might not even have enough power to complete the drilling, which would be a grave state of affairs. The Quarks' only use now is for drilling, nothing else. Toba obeys and starts to return to work. However, Rago stops him with news. Fleet Leader has rejected the use of Dulcians as slaves. None of the creatures here is to be spared. They will all die with their planet, punished at last for their defiance. Toba is pleased. The drilling is now paramount to him. The sooner it is completed, the sooner the Dulcians will die.

Jamie and Cully welcome the others to the shelter. The Doctor is last down and he has overheard Rago's report. He is very worried. Cully is saddened to learn of Balan's death, but there is more bad news to come. The Doctor tells them that nowhere on the planet is safe due to the Dominators' plans. They are not planning to extract any atomic material - they have no way to convert it. What they need is a radioactive mass ready to be sucked up and stored, just like the radioactivity here on the island was. The entirety of Dulkis is to be that mass!

The Doctor draws a diagram to explain. The 4 outer bore holes are for launching rockets through the planet's crust - thinnest here on the island. This will fracture the crust and cause a gigantic volcanic eruption. If the atomic seed device is detonated within the volcano, the entire planet will explode into a mass of molten radioactive magma. Everyone and everything on Dulkis will be destroyed.

Everyone is stunned by the enormity of it all. There seems to be no way to stop the Dominators. The Doctor says he thinks he could defuse the seed device if he could only get hold of it. Jamie suddenly brightens with an idea, but has a hard time being heard by the pensive Doctor. The centre bore hole is just outside the museum. If they can dig their own tunnel toward that bore hole, they can catch the seed device as it's dropped.

The Doctor loves the idea but worries they won't have time to complete their tunnel. Jamie and Cully volunteer to go and delay the drilling as best they can. The Doctor agrees, but wishes to have a look at the shelter's medical kit before they go.

Using the periscope, Zoe gives them the location of the hold. Jamie's ready to bash out the wall to start, but the Doctor has a better idea. Adapting his sonic screwdriver, he begins to burn out a hole in the wall.

Outside, Toba reports satisfactory progress to Rago. The drilling is on schedule. Rago reports that all the rockets have been placed. All that remains is the completion of the central bore hole.

Digging is going very well in the shelter with each person taking a turn. Jamie is impatient to get above ground and start attacking the Quarks, but the Doctor holds him back. Shortly he demonstrates the weapons he's made from the chemicals in the medical kit. He has several phials full of chemicals. To one he adds a small pill and lectures Jamie on the 10-second timing of it. At the last second, he tosses his phial and it explodes. The Doctor is very pleased. That was a small example of the larger bombs Jamie and Cully will have.

Before long, the two young men are above ground and on the hills overlooking the drilling site. They edge closer, ready to attack the Quarks. The first bomb only damages a Quark; the second destroys one. They hurry to continue from a different vantage point.

Soon several alarms are going off, indicating damage and destruction to the robots. At the drill site, Toba is ready to stop all activity and hunt down the upstart primitives. Unfortunately for the Doctor and his friends, Toba chooses this moment to remember and follow his orders. The Quarks continue drilling.

Zoe sees this through the periscope and reports it gravely. The Doctor is not surprised - the Dominators are close to their goal and will be difficult to distract. Teel has dug over 6 feet and the Doctor calls him out for a rest. Zoe is next in. They hear more explosions above them. Jamie and Cully are doing their best to help.

Rago arrives at the drill site, angry at the attack on the Quarks. Toba gives him a quick "told you so" before returning to the task at hand. The two Quarks drilling have just enough energy between them to complete their task. Rago is relieved and the drilling continues.

Jamie and Cully are getting desperate. They must delay the drilling somehow.

Zoe finishes her turn and thinks they are getting close to the bore hole. Six feet or less. Teel goes in for another turn. The Doctor still worries that they will be too late, however a very close explosion gives him hope. Zoe sees through the periscope that one of the drilling Quarks has been destroyed and the work has stopped. She is elated.

Toba is furious at this and blames Rago for not destroying the primitives earlier. Rago orders the drilling completed whilst he and the remaining energy-depleted robots seek out Jamie and Cully.

In short order, Jamie and Cully are surrounded by advancing Quarks. The only way to go is up. As they climb, the Quarks fire at them. However, the distance is too great and the low power cells of the robots impede accuracy and potency. Rago orders them to fire anyway. By luck, they manage to hit Cully.

Jamie hauls Cully to the top of the ridge. His arm is numb but he is otherwise unharmed. Jamie helps him to move as the Quarks change position.

The Doctor finishes his turn digging, saddened to hear that drilling has recommenced. There is little time left. Jamie helps Cully down into the shelter where the Doctor looks him over. His arm is paralysed but the Doctor is sure it's only temporary due to the Quarks' low power.

Zoe reports that the Dominators have finished drilling and the Doctor scrabbles into the hole. He still has a few feet to go.

Rago is pleased beyond measure with the completion of the drilling. He sends Toba to the ship to fetch the seed device. He will enjoy very much destroying this planet...and its creatures.

Jamie is digging furiously when Zoe reports Toba's return. He has the seed device. Time is nearly up. Suddenly Jamie shouts that he is through!

Toba is to prime the perimeter rockets, recall the Quarks, and prepare the ship for takeoff. Rago will drop the seed device. He orders Toba to advice the Dominator fleet to approach on their refuelling orbit.

Zoe watches through the periscope as Rago drops the seed device. The Doctor is in the tunnel but is he in time to intercept it? After an agonising moment, the Doctor emerges, triumphantly revealing the egg-shaped device. He's done it!

Everyone is thrilled, however the Doctor has spotted a new problem: the device is completely sealed. He cannot open it to defuse it. Unless he can get it off the planet very shortly, it will still explode and do untold damage. Suddenly and idea strikes - one that must be very dangerous indeed. He instructs Zoe and Jamie to return to the TARDIS and wait. Teel, Kando, and Cully must get to the travel capsule and return to the capital. He tells that that if all goes well, there will be only a localised volcanic eruption on the island, but nothing else. Everyone is full of questions but the Doctor silences them all with his urgency.

Rago returns to the ship to find all in readiness. Only two more Quarks are yet to arrive. The Dominators embark and prepare to take off.

The Doctor races across the island, barley maintaining control of the deadly seed device. He arrives at the Dominators' ship just as the last Quark enters. Sneaking up dangerously close behind the robot, the Doctor places the seed device inside the ship as the airlock door closes. He retreats and is nearly caught by the outer door, but escapes and races for the TARDIS.

The Dominators' ship lifts off.

Jamie and Zoe wait impatiently outside the TARDIS for the Doctor. He arrives just as the ship lifts off but still won't explain what he's done. There are several explosions nearby as the Dominators' rockets are launched and pierce the planet's crust. This is followed by a severe earthquake which rocks the island.

Rago and Toba are horrified to see their seed device rolling from the airlock into the control room. They can barely take in the magnitude of the situation. They think about cancelling the countdown but it is far too late.

The seed device explodes, destroying the ship and everyone on it. The Dominator threat to Dulkis is over.

The Doctor is very pleased with himself now that the danger is past. Jamie is still very concerned though about the "localised volcanic eruption". He points out to the Doctor that they are right in its path!