All four classic Doctor Who stories featuring the alien species, the Sontarans, who first appeared in the 1973 story, 'The Time Warrior'. The Sontarans are a self -cloning race who live in a militaristic society in the 'southern spiral arm of the galaxy'. Humanoid in appearance, with a squat build and distinctive dome-shaped heads, they are far stronger than mere humans and possess an unquenchable thirst for war. The other stories in this set are 'The Invasion of Time' (1977), 'The Two Doctors' (1984) and 'The Sontaran Experiment' (1975).

The Doctor (Patrick Troughton) and Jamie arrive at space station J7 to ask the Doctor's old friend Dastari to cease his experiments in time travel. The station is invaded, and when Doctor number 6 (Colin Baker) and Peri arrive, they find a shell-shocked Jamie claiming that the Doctor has been killed. It is in fact all part of a Sontaran plot to discover the secrets of time travel, which necessitates a trip to Seville to rescue the earlier incarnation of the Time Lord. Patrick Troughton's last appearance as the Doctor.