A ship sets down on a remote island on the planet of Dulkis. From the ship emerge two men, Dominators Rago and Toba, and their robot servants - quarks. Toba confirms that the local radiation has been absorbed and transferred to their energy banks. They need much more though, for their own ship and for the other ships in the fleet: that is why the have come to Dulkis; Rago observes that the locals would provide a slave labour force - to be destroyed only if necessary.

Cully and a group of friends are approaching the island - just for an adventure. The island has been uninhabited for 170 years, nothing can live there because of the fallout. Conventional travel is not possible without a permit so Cully and is party have approached the island in a manually operated ship. His passengers berate him for his overdramatisation - there is a survey station on the island, monitoring the radiation and students come every week to see the horrors of atomic war. They also challenge his statment that they are near the island - the images they are looking at could be from any library. Lack of a radiation warning results in the ship getting too close to the island and it ends up crashing ashore. A check of the radiation shows a zero reading and so the conclusion is that Cully's navigation was off and they have arrived on another island and not the Island of Death! When they encounter the Dominators though, they are confronte with more adventure than they had anticipated.

The Doctor has brought Jamie and Zoë to Dulkis because it is a peaceful planet. As explosions sound and the Dominators begin to carry out their plans, the travellers are thrown into another fight to save a planet from destruction.

As problems beset the TARDIS, the Doctor is faced with the possibilty that the TARDIS might not be safe from a closing flow of lava. Using an emergency system, the Doctor takes the TARDIS outside of normal space and time, in fact outside of reality altogether. The TARDIS stabilises, but there are no readings on any of the instruments. The Doctor decides to go to the power room to check on the systems: he informs Jamie and Zoë that the TARDIS is nowhere. His fear is that outside the TARDIS they would all be at the mercy of whatever forces exist beyond time and space.

Jamie is checking the scanner and sees that the TARDIS has arrived in Scotland. When Zoë arrives the scanner has gone blank - probably just mist. However, when Zoë looks on the scanner she sees her home city. While Jamie goes to get the Doctor, Zoë opens the TARDIS door and goes outside. Realising that the images were put on the scanner to tempt the travellers outside, the Doctor is horrified to find that Zoë has left the safety of the ship. Jamie runs out to rescue her, while the Doctor comes under attack from some force that penetrates the TARDIS.

Materialising in orbit around the Moon, the TARDIS comes under attack. The Doctor just manages to relocate the TARDIS and they arrive on Earth. If they have arrived in the correct time zone, they might be able to get the assistance of Professor Travers in repairing the damaged components from the TARDIS. Coming to a road, they arrive in time to hitch a lift from a lorry. The driver seems abrupt with them and after a while he stops the lorry and urges them to get out and away from the lorry. As the four people hide, the driver explains that he is trying to escape from the compound. Its a community of factories and houses and the people there are all members of the company, International Electromatics. Getting out of the compound is difficult, especially if you are not or do not want to be a member of the company. Returning to the lorry, the driver takes the travellers to a place outside the compound. Bike riders are close behind and when they catch up with the driver they try to take him back to the compound. When he refuses the bike men shoot him dead.

The Doctor, Jamie and Zoë get another lift into London where they go to Travers' house...but find it occupied by Isobel Watkins. Her uncle has taken over the flat from Professor Travers. On further questioning it transpires that Professor Watkins might be able to help the Doctor. However, Isobel has not seen her uncle for a week and all attempts to contact him have failed. When the Doctor learns that Watkins is working for International Electromatics he decides that further investigation is warranted.

Every so often, two of the brightest and the best of the Gonds are chosen to become companions of the Krotons. Now Abu and Vana have been selected. Thara does not wish Vana to go and while they argue, Abu accepts his honour and enters the machine of the Krotons. The Doctor, Jamie and Zoë are exploring when they notice a city nestling near the foot of a vast sphere. They find a doorway leading inside the machine but as the door opens they take cover. They watch in horror as a young man staggers out of the doorway only to be vaporised seconds later. The travellers move away from the doorway and head on into the city where they are stopped from interfering in an important ceremony. They witness a young woman passing through a doorway: a doorway similar to the exit they had seen earlier. And the woman is wearing a cloak and amulet similar to that worn by the young man they saw being vaporised.

The Doctor and his friends run quickly to the exit and are able to rescue the woman from the vaporising jets. Now the Gonds are faced with the terrible reality that their brightest and best appear to have gone to their deaths over the years. As the exit is in a wasteland considered deadly none of the Gonds have ever discovered this. The Doctor concludes that over time the poisons of the wasteland have faded. The wasteland was made so when the Krotons first arrived. Given their immense power and the fact that they teach the Gonds, why would the Krotons kill the most intelligent? Even the knowledge which has been passed on to the Gonds is incomplete. There are significant gaps as if the Krotons are selective in wwhat they want the Gonds to learn. The Krotons have remained inside their machine for centuries but with some of the younger Gonds now questioning the benefits bestowed upon them they begin attacking the machine. How long before the Krotons re-appear and what fate might befall all of the Gonds if they do?

At the latter end of the 21st century, conventional transportation around and even beyond the Earth has been supplanted by T-Mat - a form of instantaneous travel where people and cargo can be transmitted from one place to another. The relay station is based on the Moon - but a hitch during one transmission has resulted in a backlog, something which Miss Kelly is not happy about. The blame appears to lie upon Fewsham and when the supervisor, Osgood arrives, Miss Kelly remarks that Fewsham is evidently not up to the job. Agreeing, Osgood uses the T-Mat to go to the Moon.

Just as Osgood starts to sort the situation out, the outer airlock is opened. Something enters the base: and when these alien arrivals coerce Osgood into using T-Mat for them, he sabotages instead. His defiance costs him his life. With T-Mat out of operation, people and cargos on earth are unable to get to their destinations. Head of the T-Mat section in London, Commander Radnor concludes that somehow they must get to the Moon and repair T-Mat. Miss Kelly points out that without T-Mat they cannot get to the Moon, but Radnor knows of another way...

The Doctor, Jamie and Zoë emerge from the TARDIS into a space museum. They marvel at the various rockets and spacesuits and other devices. The owner of the Museum, Daniel Eldred is not happy at their intrusion and even believes them to be there for a laugh. The arrival of Radnor convinces him that these intruders are some of his friends. It soon becomes clear that Radnor is there because Eldred has been building a rocket. Now they need that rocket to get to the Moon and find out what is wrong with T-Mat. Eldred is too old and no-one is trained to fly the rocket - so the Doctor volunteers. Once they get to the Moon they can sort out T-Mat...except that they soon discover that is not only problem they will face.

Beacon Alpha One is approached by a spaceship: the ship docks; figures emerge from the ship and begin offloading equipment and attaching explosives and rockets to various sections of the station. The task complete, they return to their ship and undock. From a distance they detonate the explosives and the space beacon fragments. General Hermack suspects that the silence from the beacon can only be the result of piracy. All such beacons are built from argonite, also this sector is known for raids on ships containing argonite. Hermack decides that they will visit the region of the beacon to investigate its silence. They arrive in time to see a pirate ship towing off the fragments of the beacon. Unfortunately they are unable to catch up with the pirates and lose them.

The TARDIS materialises inside a space beacon. As the travellers explore the beacon they run into armed men, separating them from the TARDIS. The Doctor, Jamie and Zoë end up in another, sealed section of the beacon. When the pirates arrive they begin to carve up this station as well and it looks as if the travellers are trapped in a section with no escape.

The Doctor, Jamie and Zoë explore their latest destination: a barrage and gunfire traps them in a foxhole until a passing ambulance, driven by Lady Jennifer offers them an escape route. German soldiers capture all four of them and force Lady Jennifer to drive them to the German lines. Thankfully a troop of British soldiers intercept the ambulance and rescue them. Next stop: the British trench. The Doctor, Jamie and Zoë decide that they must get back to the TARDIS and away from this terrible period in Earth history. As soon as the firing quietens down, the Doctor pops his head over the trench wall - and narrowly misses being shot. He explains to a soldier that he was trying to get to his transport, but the soldier remarks that all that lies that way is the enemy. Major Barrington wonders about these civilians found in No Man's Land and so he alerts General Smythe. Smythe wants them brought to him for interrogation. While he is waiting, he goes to his private room and operates a television-like device.

The travellers are put on a supply truck to be taken to their meeting with General Smythe. At first, it appears that the general is not in his room and so the travellers will have to wait. Then he emerges from his room even though Captain Ransom was sure it was empty moments before. When the Doctor, Jamie and Zoë are brought before Smythe he has them charged with spying and desertion. As a spy, the Doctor will be shot, Jamie will be returned to the regiment he deserted from and Zoë will be sent to prison. It appears to the Doctor that Smythe has a strange influence over his subordinates...and its as if he wants the travellers out of the way.