Season 20
Structurally, the season retread season 18's formula of including a trilogy of stories bound together by an overarching theme. In this instance, the tripartite tale involved Turlough's attempts to kill the Doctor at the behest of the Black Guardian.
198322 EpisodesDrama, Action & Adventure, Sci-Fi & Fantasy
Episode Guide
On Gallifrey, someone on the high council is perpetrating a treasonous act - transmitting the Doctor's bio-extract from the space/time matrix to an anti-matter being. On Earth, two English lads spend their last night in Amsterdam sleeping in a crypt where they're attacked by an alien creature under the same anti-matter being's control.