The Invisible Enemy

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"

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