Aided by his two assistants Jamie and Victoria, the Doctor lands the TARDIS on Telos, last resting place of the infamous Cybermen. There he discovers a band of archaelogists on a secret expedition to unearth the reason for his old enemies' extinction. In the underground shadowy depths, they find the icy tomb. A whole army in hibernation. A threat to no one, if the temperature remains low. But if the traitor in their midst gets his way, things could really heat up.

The Doctor's TARDIS lands at the Snowcap space tracking station in Antarctica in December 1986. A routine space mission starts going wrong. When the base personnel's suspicions are roused, the Doctor informs them that the space capsule is being affected by the gravitational pull of another planet — a tenth planet in the Solar system.

The Second Doctor and Jamie arrive on what appears to be a space station called the "Wheel in Space" it's here that they meet Zoe Herriot a young parapsychology librarian, The Doctor hits his head concussing him leaving Jamie and Zoe to defend off the Cybermen from taking over "The Wheel in Space."

The Doctor, Jamie and Zoe return to Earth and become embroiled in the schemes of Tobias Vaughn. They meet up with an old friend, Colonel (now Brigadier) Lethbridge-Stewart, and some old enemies, the Cybermen.

The TARDIS arrives in London in 1966 and the First Doctor and Dodo visit the Post Office Tower. There they meet Professor Brett, whose revolutionary new computer WOTAN (Will Operating Thought ANalogue) can actually think for itself and is shortly to be linked up to other major computers around the world — a project overseen by civil servant Sir Charles Summer.

The TARDIS arrives in 2070 on the Moon, where a weather control station under the command of a man named Hobson is in the grip of a plague epidemic — in reality the result of an alien poison planted by the Cybermen. Jamie is knocked unconscious and lapses into a delirium, leaving the Second Doctor, Ben, and Polly to fight off a massive Cyberman attack.

The waters surrounding an island become contaminated by chemical dumping, and people who eat fish caught in those waters become deformed and violent.

The Doctor and his companion Evelyn investigate a series of mysterious disappearances on the planet Chronos and once again encounter the dangerous Cybermen.

A condensed, 10-minute animated reconstruction of the first episode of the 1968 Doctor Who serial The Wheel in Space, using the original TV soundtrack.