Written by Bob Baker and Dave Martin
"Some kind of organism that attacks the mind, the intelligence. It's trying to take me over, Leela. It's trying to change me"
| Episode Title | Premiere Date |
| Episode 1 | 01/10/1977 |
| Episode 2 | 08/10/1977 |
| Episode 3 | 15/10/1977 |
| Episode 4 | 22/10/1977 |
The TARDIS picks up a mayday message, but before the Doctor and Leela can fully respond, the police box also passes through the mysterious cloud and the Doctor falls victim to a strange virus. As the situation worsens, his only hope lies in the unlikely combination of the eccentric scientist Professor Marius, and his dog-shaped computer, K9...
Cast & Crew
The Doctor: Tom Baker
Leela: Louise Jameson
K9 (voice): John Leeson
Lowe: Michael Sheard
Professor Marius: Frederick Jaeger
The Nucleus (voice): John Leeson
Marius' Nurse: Elizabeth Norman
Producer: Graham Williams
Director: Derrick Goodwin
Scriptwriters: Bob Baker and Dave Martin
