The Invasion of Time

TV Season 15, Serial 6

Aired: 4 February 1978 - 11 March 1978

Another episode set on Gallifrey, the return of the Sontarans, and the introduction of the Vardans. Leela and K-9 decide to stay on Gallifrey with Andred, which leads to the Gallifrey series. This is the end of Season 15.