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.