Viner is worried about the explosives that have been planted into the hillside to enable the team to gain access to the tombs of the Cybermen. There can be no telling what affect the rarified atmopshere of Telos could have. The detonation goes ahead and at first it does not appear to have made any difference. As the dust settles though the team of archaeologists and logicians make out a set of doors. The next step is to open them: Kaftan ofoffers money to the first person to open the doors. A member of the crew of the rship that brought them there tries - and is killed by an electric field running through the door. Before the team can think on what is happening they hear the sound of something, some kind of ship perhaps. The Doctor, Jamie and Victoria appear shortly afterwards - evidently they are a rival expedition.

The Doctor determines that the charge has been drained and so the doors can be opened safely. Jamie struggles to move the massive doors: Toberman, Kaftan's assistant grabs the handles and opens the doors - now the Tombs are open. Or rather they are in an upper control room with two doors leading to other rooms and a hatch which leads down. With a bit of help from the Doctor, Kleig opens the two doors and the team splits up. Haydon and Jamie try the first door; Kaftan, Viner and Victoria go through the other door; the crew of the ship return to their ship; the Doctor remains in the control room with Kleig and Parry. Toberman wanders off on a mission of his own...

Viner's party find a room which appears to contain equipment the Cybermen would use for recharging themselves; Kaftan traps Victoria in a recharging unit and Viner struggles to find a release mechanism. Jamie and Haydon find a room with a control panel. The panel appears to operate a series of lights and through trail and error Haydon concludes that there is one switch left to try. He urges Jamie to press it...and a Cyberman emerges from hiding, and Haydon is shot dead. It would appear that the Cybermen are not so dead after all...

Edward Travers is a member of a British expedition to the Himalayas, in search of the Yeti. Something attacks his camp leaving him the sole survivor. He escapes and obtains refuge at the nearby Det-Sen monastery. According to Travers he was attacked by the Yeti: when a man dressed in a thick coat arrives, carrying a rucksack from the campsite Travers and suggests to the monks that a man in a fur coat, in the dark, might easily have been mistaken for a Yeti. Travers assures the man, the Doctor, that the monks will do him no harm. In the meantime, with the Doctor locked up, Travers can continue his search for the Yeti - he believes that the Doctor is a member of a rival expedition.

Jamie and Victoria have been left behind in the TARDIS: at first the Doctor had been keen for all of them to go the nearby monastery of Det-Sen, to return the holy ghanta, a relic entrusted to him many years before. Assuring them that they would all be afforded the welcome of a lifetime, the Doctor had gone outside, leaving Jamie and Victoria to search for the ghanta in one of the TARDIS chests. After he had wandered around outside, the Doctor changed his mind and headed off to Det-Sen alone, taking with him the now found holy ghanta. Naturally, as soon as the Doctor is out of sight, Jamie and Victoria leave the TARDIS. There are strange footprints near the TARDIS which they decide to investigate.

Phase 1 evacuation procedure is being announced at Britannia base: the base ioniser has been allowed to deteriorate to danger levels; Clent urges Miss Garrett to stabilise the ioniser; they just manage to do so - and she warns Clent that they need Penley. Clent remarks that Penley is no longer a member of the team. Reports from other bases show that the glaciers are being held around the world, but if the ioniser at Britannia fails then the rest will follow. To add to his worries, Clent is annoyed to find out that another scientist, Arden, is still outside at the ice face. Arden is more interest in something within the ice - a mammoth or something? As he prepares to drill into the ice face, Arden sees something that looks like a warrior.

The TARDIS has materialsed next to a wall of ice, or that is the initial impression. Noting that it is actually part of some artificial structure, the Doctor, Jamie and Victoria also spot two men making a hasty exit from within the structure. The travellers enter the structure and find their way into the base. A member of the base staff pins evacuation badges on them. The Doctor overhears the pitch of a computer and notes that there is something wrong. Clent is alarmed at their presence and tries to have them removed, but the Doctor warns that if nothing is done within the next two and half minutes there will be an explosion. He hurries around, giving instructions and thankfully stabilises the situation - impressing Clent.

When Clent takes a break, Arden arrives with his find - a warrior-like man, buried in the ice. The strange thing is that he looks like some kind of pre-Viking warrior...with armour. Unlike anything ever discovered before.

The TARDIS has materialised on a beach, much to the Doctor's delight. He urges Jamie and Victoria to have a look in the ship for buckets and spades - to make sandcastles. They leave the Doctor to enjoy a paddle in the water, preferring to stay by the TARDIS. A small party of men on a hovercraft are watching and when they observe the Doctor through the binoculars, they contact Astrid and make it clear that they intend to take the chance to kill this man. Astrid checks with Kent and he urges her to stop them, but by now the men are out of contact.

Astrid arrives as the men on the hovercraft are shooting at the Doctor, Jamie and Victoria. She rescues them amid the shooting and flies them to a bungalow further inland. Her fear is that the fuel tank has been hit. Once there, the Doctor tends to Astrid's wounds - at least one bullet hit her. During the conversation the Doctor asks why those men were trying to kill him and his friends. Astrid informs the Doctor that he was their target: they hate the person they think he is - the Doctor resembles a ruthless dictator determined to take over the world - Salamander. The men in the hovercraft arrive - there is no time to explain to them that the Doctor is not Salamander. At Astrid's suggestion, the Doctor is taken to meet her employer - Giles Kent. He is astounded at the resemblance between the Doctor and Salamander.

Showing the Doctor a broadcast made by Salamander the resemblance is evident. However, in his speech, Salamander talks about projects that are benefitting the needy - he is saving the world from starvation, among other things. Kent states that Salamander is doing all this to further his own ends, to become ruler of the world. The Doctor needs proof, more than just words of a man who has good reason to resent Salamander. Given their resemblance to one another, the Doctor could assume Salamander's identity and find out more from the inside...

Anne Travers arrives at the house of Julius Silverstein to mediate between him and her father, Professor Travers. Professor Travers wants Julius to return the deactivated robot Yeti he sold him years ago because it is dangerous. It has stood in Julius's private museum for 30 years, doing nothing - so how can it be dangerous. Travers explains that he has been working on a Yeti control sphere for years and now he has activated it...but the sphere has disappeared. Anne persuades him to go back home and search for the sphere - he has been known to misplace things before. Glad that Travers has gone, Julius prepares to close down for the evening. Then he hears a window breaking. Investigating, Julius watches as the robot Yeit that has stood there for 30 years comes to life - then it kills him.

After stabilising the TARDIS, the Doctor sets course, though Jamie and Victoria surmise that he has little idea of where and when they will end up next. The TARDIS materialises in space, suspended - which puzzles the Doctor. As they watch the scanner, some strange substance envelopes the TARDIS - presumably part of the force which is holding them there. The Doctor attaches a device to the console though it won't do anything until the TARDIS resumes its flight. After a wait, the substance begins to fade and the Doctor quickly operates the controls and the TARDIS lands properly. The device has enabled the Doctor to land the TARDIS about half a mile from where they were meant to arrive. Finding themselves in the London Underground, the travellers look for a way out. All exits to the surface, at one they find the web-covered body of a newspaper vendor. The tunnels seem to their only hope: thankfully the electricity is off so the rails are not live. In fact, a layer of dust suggests they have not been in use for some time. Spotting some cabling, the Doctor follows it while Jamie and Victoria hide. They are caught by some soldiers and taken to an underground base, their fortress.

Professor Travers has also been brought to an underground base by the army, at the request of his daughter Anne. It is hoped that between them they can combat the menace that has taken over central London: a strange impenetrable mist above ground; and a web-like substance that is gradually blocking off the underground. There one hope is to stop the flow of this web by blowing up the tunnels...and the cabling the Doctor is following leads to one of the sites selected for demolition!

Once again, the Doctor, Jamie and Victoria finds themselves on a each. Lots of foam is on the shore - quite normal, Victoria assures Jamie, but the Doctor believes that the volume of foam is far from normal. Nearby they spot a pipe emerging from the sea, and a box attached to part of the pipe. A strange noise can be heard from the pipe, like the sound of a heartbeat. Could it be a pump of some kind? After all it is part of a gas pipeline. An observer from nearby shoots at the three travellers. When they awaken later the Doctor, Jamie and Victoria find themselves under guard in some kind of control room. Chief Robson asks them why they were in a restricted area - they were seen tampering with the emergency release control - are they saboteurs? Not satisfied, Robson orders the travellers be confined for the time being. There have been problems, including loss of pressure on a pipeline - so the travellers are prime suspects for these mysterious events.

Harris is told to escort the Doctor, Jamie and Victoria to a holding room. Once there, the Doctor suggests to Harris that the noise he heard could be because something has gotten into the pipes. Or there may be a breach? Perhaps the pipeline should be shut down pending an investigation? Harris remarks that Robson would do no such thing. He takes pride in maintaining the flow of gas.

As communications with other rigs become sporadic and other members of Robson's team report the sounds coming from the pipeline it becomes apparent that something has indeed gotten into the pipeline.

A fault in the TARDIS forces the Doctor and Jamie to escape from the ship. Exploring their surroundings they find that the TARDIS has materialised inside an apparently empty spaceship, drifting through space. Somewhere on this ship, hopefully, they will be able to find some mercury to replace the leakage from the fluid links. Until they do, Jamie and the Doctor cannot return to the TARDIS. A search of the ship reveals nothing. So they try to gain access to the control room of the spaceship. Using a food machine located during their search, the Doctor and Jamie have something to eat. Jamie goes to sleep so the search for the control room is put on hold.

Noticing a series of tracks in the corridors of the spaceship, the Doctor heads for the control room. The rocket begins to manoeuvre - but when the Doctor and Jamie try to get back to the TARDIS they find that the door to that section of the ship has been sealed. A servo robot monitors the movement of the ship and oversees the launch of some spheres. The ship is also approaching a space station. The movements of the ship has caused the Doctor to hit his head and he becomes erratic.

The space station is monitoring the spaceship - it has been registered as missing for nearly two months now. Even accounting for drift the ship should not be in this sector of space. All attempts to communicate with it have failed. With no signs of life and with the ship poposing a possible hazard to the station, it looks as if there may be only one choice - to destroy it.