This DVD stars Colin Baker as the Doctor, who (along with his travelling companion Peri) investigates a mysterious distress call from 1985 Earth, the maker of which turns out to be the ex-Dalek agent Lytton, who has a new master... the Cybermen. After luring them in to the sewers, the Doctor and Peri are captured by the Cybermen, who want to use his time machine to change history and make Halley's Comet crash in to Earth before it destroys their home planet Mondas.