Searching for the sixth segment, the Doctor and Romana land in the midst of a brutal nuclear war between the planets Atrios and Zeos.
The Doctor and the Shadow have their final confrontation to take control of the Key to Time. The Black Guardian will do anything to obtain it and plunge the Universe into chaos.
The Doctor meets a new enemy, the Shadow, who wants the Key to Time. Also, the Atrian-Zeon war is approaching an awful climax.
