The TARDIS materialises on the planet Telos, where the Doctor and Jamie come across a group of archaeologists who are attempting to discover why the Cybermen have seemingly disappeared.
The Doctor and Jamie are thought to be from a rival party, but as the archeological party's craft is disabled they join forces. They start to look around a Cyberbase. Apart from a dead target there are no signs of the Cybermen.
One of the members tries to open the Cybermen's tomb, but is unsuccessful, until the Doctor unwittingly provides him with the answer. Underground, and frozen, they discover the Cybermen, entombed.
Klieg plans to thaw the Cybermen, and thinks he can control them, but the Cybermen are prepared and use Cybermats to attack the people. The Cybermen plan to convert all who are present into Cybermen, and nearly convert Klieg's servant Toberman.
The Doctor, Jamie, Victoria and the archaeological party manage to get out of the Cyberbase, and Toberman closes the electrified doors. When the door closes Toberman is electrocuted, but the Cybermen are trapped once again.
