The TARDIS, with the Fifth Doctor, Tegan, and Turlough on board, becomes caught in a time corridor. Once freed, it materializes in London in 1984, near the exit of the corridor. Upon investigating warehouses nearby, the travelers stumble upon a trap set for them by the Daleks. Meanwhile, in the future at the other end of the time corridor, a Dalek battle cruiser attacks an obsolete Earth prison station in deep space to free Davros, their creator. Held in suspended animation aboard the station for over 90 years, the Daleks aim is to get his help in finding an antidote to a virus deadly only to Daleks. The virus was created by a race of humanoid robots called Movellans, who have been at war with the Daleks for centuries. Upon revival, Davros learns that the Daleks have been almost wiped out and are now being systematically hunted down and destroyed by the Movellans. To counter the offensive and in an attempt to save themselves, the Daleks use their time technology to infiltrate key positions of authority on Earth with android duplicates. Having now also lured and trapped the Doctor to copy his brain pattern, they intend to send duplicates of the Doctor and his companions to Gallifrey. On arrival, the duplicates would kill the High Council and gain mastery over time, wiping out all their past defeats. Ultimately, their plans are thwarted when the Movellan virus is deliberately released on board the station by Davros as his Daleks led by the Supreme Dalek turn against him yet again. Back on Earth, the Doctor also releases the virus, destroying the Daleks there, and Davros flees the station in an escape pod.