Two city maintenance workers in the London sewers are attacked by something upon finding a wall where there shouldn't be one. Elsewhere, former Dalek taskforce commander Lytton and three criminal associates -- Griffiths, Payne and Russell -- plan to rob a diamond merchant's, but Lytton surprises them all by telling them that the heist will take place today. Despite the short notice, Russell reluctantly contacts his supplier and demands seven kilos of plastique.
The Doctor, dismissing Peri's claims that he's taken on too much work after his erratic regeneration, repairs the TARDIS' chameleon circuit and decides to take his companion somewhere she can relax. Instead, the TARDIS goes out of control and materializes near Halley's Comet in the year 1985. The Doctor sets about repairing the fault, while Peri worries that the TARDIS could collide with the comet if anything else goes wrong. On Earth, comets are always associated with impending disaster...
Lytton's gang enters an abandoned scrap merchant's, where Lytton checks on a nearby transmitter while Payne breaks into the sewers. Lytton intends to traverse the sewers and use Russell's explosives to break into the diamond exchange; the vibrations will set off every alarm on the block, and the police won't know where to start looking until too late.
The TARDIS picks up an intergalactic distress call from Earth, and the Doctor traces it to London. The TARDIS materializes in its old haunt, Foreman's Yard (much to the Doctor's amusement once he realizes), where it takes on the form of a Victorian kitchen range. Peri is still worried about the Doctor's mental stability, but he insists that he's all right, and traces the source of the signal to an abandoned building. There, he realizes that the signal is being bounced around several relay points throughout London; the alien is obviously wary and wants advance warning if its signal is detected. The Doctor and Peri return to the TARDIS to trace the transmitter, unaware that they've been observed by the two silent policemen who served under Lytton during the Dalek incident. The TARDIS materializes in the scrap merchant's in the guise of an old pipe organ, and while exploring, the Doctor and Peri are attacked by the two policemen. They overpower the policemen and handcuff them to the walls, and then enter the sewers through the entrance Payne made earlier.
Russell senses that they're being followed, and Payne stays behind to guard the gang's backs. But the creature which attacked the maintenance workers surprises and kills him. Lytton, Griffiths, and Russell reach their destination, where Russell finds the wall which shouldn't be there -- and a Cyberman emerges from the shadows. Russell panics and flees while Griffiths opens fire, puncturing the Cyberman's hydraulic valves. Lytton then holds Griffiths at gunpoint as the false wall slides open to reveal a patrol of Cybermen. Lytton surrenders to the Cyber Leader, and Griffiths is captured as he tries to flee. The Doctor and Peri hear the gunfire and screaming, and stumble across Payne's body while rushing to investigate. The Doctor takes Payne's gun, which was never fired.
The captured sewer workers -- and Lytton's two policemen -- are being converted into Cybermen. Lytton talks his way out of the same procedure, explaining that he detected the Cybermen's transmissions and deliberately contacted them, bringing along humans for them to convert as a sign of goodwill. He identifies himself as a warrior mercenary from Riften V and points out that he could easily have alerted Earth authorities to the Cybermen's presence but chose not to. The Cyber Leader accepts the logic of his argument and decides to report to the Controller on Telos.
On Telos, a work party of slaves plants explosives in the ground. Three of them make a break for it, but one is killed and the decapitated Cyber-head which they require for the next stage of the escape is destroyed. The two survivors, Bates and Stratton, hide nearby, but without a third pilot and a Cyber-head, they're still as good as prisoners. The other slaves' spirits have been completely crushed; nobody else has tried to escape. In Cyber Control, the Controller receives a report of the escape attempt, and decides to analyse Bates and Stratton's behaviour as they attempt to survive and escape.
The Doctor and Peri are captured by Russell, who frisks the Doctor and finds Payne's gun. The Doctor manages to surprise and overpower Russell, who eventually admits that he's an undercover policeman who infiltrated Lytton's gang to find out who he was. After a raid on an electronics warehouse -- which the Doctor and Peri realize supplied Lytton with the parts he needed for his intergalactic transmitter -- the police heard Lytton's name whispered on the streets, but could find no records of his existence at all. It was as if he'd just arrived from another planet. The Doctor warns Russell that this is exactly what he did -- and he's a ruthless, professional killer...
Bates and Stratton use their mining tools to destroy and decapitate a Cyberman sent out to recapture them. Bates intends to clean out the head so Stratton can use it as a disguise; as prisoner and escort they stand a better chance of getting into Cyber Control. But the destruction of the scout is detected, and the Controller decides that Bates and Stratton are too resourceful and must be destroyed.
Back on Earth, the Cybermen detect temporal distortion nearby, and send scouts to investigate. The Doctor, Peri and Russell encounter one, and the Doctor destroys it by plunging his sonic lance into its chest unit. The Cybermen detect this, and the Leader decides to close down this base and send the partially converted humans to their mothership. The Leader himself takes a squad out to investigate the scout's destruction, and when they find an alien artefact was responsible Lytton soon guesses who the "alien" is. He's surprised to learn that the Cybermen already know of the Doctor. The Cyber Leader decides to alter his plans and capture the Doctor and his TARDIS.
The Doctor, Peri and Russell emerge from the sewers, closely followed by the Cybermen. But the Doctor has accidentally left the TARDIS doors open and Cybermen have already entered the ship. Russell destroys one by shooting it through the weak point in its mouth panel, and shoots another with the first Cyberman's gun. But before Peri can shut the doors the Cyber Leader and his patrol arrive, and while Russell is distracted a third Cyberman emerges from the corridors and strikes him, instantly snapping his neck. The Cybermen then close in on Peri...
The Doctor threatens to destroy the TARDIS unless the Cyber Leader agrees to spare Peri's life. He does so, giving the word of the Cyber Controller that she will not be harmed -- and the Doctor realizes that, by implication, not only did the Controller survive their last meaning but these Cybermen have somehow travelled through Time. He sets the co-ordinates for Telos, and he, Peri, Griffiths and Lytton are locked up in a nearby storeroom. Lytton returns the Doctor's sonic lance so he can sabotage the navigational controls and shift the TARDIS slightly off course, and reveals that the Cybermen haven't developed their own theories of Time travel; they simply stole a ship which was forced down on Telos for repairs. The Doctor, attempting to explain the history of the Cybermen to Griffiths and Peri, is forced to admit that their home world Mondas was destroyed while attacking Earth -- in 1986, which in their terms is next year. The Doctor assures them that Earth survived with minimal damage; the surviving Cybermen evacuated to Telos, wiped out the indigenous Cryons and transformed their refridgerated cities into cryogenic tombs in which to hibernate and recover their strength. Bates and Stratton continue to approach Cyber Control despite Stratton's conviction that the plan will never work. The reactivation of dormant Cybermen is halted when too many are found damaged or dead; some are going rogue in the tombs and destroying everything they encounter.
The Doctor is forced to switch off the distress call he'd surreptitiously activated, but thanks to his earlier sabotage the TARDIS (in the form of a set of iron gates) materializes in the tombs rather than in Cyber Control. While the Cyber Leader reports for further instructions, the Doctor notices a stench of decay in the air -- and realizes that Lytton knows more about it than he's saying. A rogue Cyberman suddenly bursts out of a tomb and attacks them, and in the confusion Peri, Lytton and Griffiths escape. Peri, separated from the others, is attacked by yet another rogue Cyberman -- and is rescued by two Cryons...
Griffiths and Lytton hide in the tunnels outside the tombs, where they are contacted by a Cryon named Threst -- who welcomes Lytton by name. Lytton admits that he's been working for the Cryons all along; it was they who picked up his distress call from Earth, and on their behalf he intends to steal the Cybermen's time machine. Since the Cryons can only survive in sub-zero temperatures they will be unable to help, and Lytton thus brought Griffiths along to act as his bodyguard, in return for which the Cryons will pay him the equivalent of two million British pounds in uncut diamonds. Griffiths is reluctant to risk his life, but Lytton points out that his only two alternatives if captured are death -- or conversion into a Cyberman.
The Doctor is locked up in a storeroom with a Cryon prisoner, Flast, and upon learning that some Cryons survived the Cybermen's attempt at genocide he also realizes that they must be responsible for the damage to the Cybermen in the tombs. He's less pleased by Flast's revelation of the Cybermen's plans -- since they stole their time machine they don't fully understand the principles of Time, and intend to change history by preventing Mondas from being destroyed...
Lytton and Griffiths emerge onto the surface of Telos, where they are confronted by Bates and Stratton. Griffiths is shocked to learn that Bates and Stratton are partially cybernetic; they were sent to the work parties when the conversion process failed. Lytton points out that the time vessel requires a crew of three and suggests that they join forces. Meanwhile, Peri is held in the Cryon base by Rost and Varne, who are unable to help her rescue the Doctor as they would perish in the heat of Cyber Control. They admit that Lytton is working for them to prevent the Cybermen from leaving Telos -- upon abandoning the planet the Cybermen intend to destroy it to observe the effect on its atmosphere.
Flast explains to the Doctor that the Cybermen intend to divert the course of Halley's Comet, causing it to collide with Earth. The Doctor suddenly realizes that the Time Lords have once again manipulated him into this situation so he can clean it up for them. Flast points out a potential weapon; the storeroom contains canisters of vastial, an unstable mineral which explodes upon reaching fifteen degrees above zero, and she's managed to open one. The Doctor uses his sonic lance to pick the lock of the storeroom door, and uses a small amount of vastial to destroy the guard outside. Flast takes the sonic lance, turns it on and buries it in the open canister of vastial, hoping to spark an explosion which will destroy Cyber Control. She is unable to leave the sub-zero storeroom but urges the Doctor to escape without her.
Lytton and his companions enter Cyber Control, but as Lytton is guarding their backs he is attacked and overpowerd by Cybermen and the others have no choice but to carry on without him. Lytton is taken back to the control room and tortured, and when he refuses to speak he is taken to be converted into a Cyberman. Rost and Varne learn of Lytton's capture while taking Peri back to the TARDIS.
The Doctor returns to the TARDIS, where he finds two Cybermen on guard and is reunited with Peri. Rost and Varne help him break into a tomb which they have already sabotaged, and the Doctor activates the distress call in the dead Cyberman inside, luring the two guards away from the TARDIS and into a trap. In the ensuing battle, Varne is killed but both Cybermen are destroyed. As the Doctor prepares to leave, Peri insists that they rescue Lytton first, and the Doctor, who was fully prepared to leave Lytton to his fate, is startled to learn that he was working for the Cryons all along. He agrees to see what he can do.
Bates, Griffiths and Stratton finally reach the landing pad, but just as they're within sight of their goal Bates is killed by an electrified door -- which opens to reveal a Cyberman who guns down Griffiths and Stratton. Meanwhile, the Cybermen detect the Doctor's escape and question Flast; when she refuses to speak they fling her into the corridor, where her body boils away in the heat. As the Cybermen begin checking the vastial stores, the Cyber Controller learns that the TARDIS has been moved and returns to the control room. The sabotaged vastial container, hidden in the back of the storeroom, has begun to steam...
The TARDIS, once again in the form of a police box, materializes in the control room. The Doctor emerges to find Lytton partially converted, and as he tries to free him from the processing machine Lytton, drugged and partially converted, begs the Doctor to kill him. The Cyber Controller arrives, having guessed that the Doctor's emotional weaknesses would draw him back to rescue his friend. As the Controller approaches, however, Lytton attacks him, puncturing his hydraulic valves with the knife the Doctor was using to pry him free from the processing machines. The Controller strikes back, snapping Lytton's neck, while the Doctor grabs the Controller's gun and shoots the Cyber Leader, who staggers back into his Lieutenant, causing him to accidentally shoot both himself and the Leader (again). The Doctor then shoots the Cyber Controller, destroying him once and for all. Peri emerges from the TARDIS and practically drags the Doctor away from Lytton's body.
As the TARDIS dematerializes, the sonic lance finally heats the vastial to ignition point, and the resulting chain reaction destroys all Cyber Control and the stolen time machine as well. The Earth is safe and the web of Time has been preserved... but at a great personal cost, as the Doctor blames himself for misjudging and failing to save Lytton.
|Source: Cameron Dixon