The 545th episode of Doctor Who airs on BBC1. This story brings the E-space trilogy to a close and is written by science fiction novelist Stephen Gallagher. Clifford Rose and Kenneth Cope guest star. This episode is the final appearance of Lalla Ward as Romana. K-9 also permanently leaves the series as of this episode, but due to the character’s popularity, steps are already being taken to create a spinoff for him.