30 October 1976
Tom Baker (Doctor Who)
Llewellyn Rees (The President) [1-2], Bernard Horsfall (Chancellor Goth), George Pravda (Cardinal Borusa) [1-2, 4], Peter Pratt (The Master), Hugh Walters (Commentator Runcible) [1-2], Erik Chitty (Co-ordinator Engin), Derek Seaton (Commander Hilred) [1, 2, 4], Maurice Quick (Gold Usher) ; John Dawson [1-2], Michael Bilton  (Time Lords); Peter Mayock (Solis) , Helen Blatch (Voice) *.
|Written by||Robert Holmes|
|Directed by||David Maloney|
|Produced by||Philip Hinchcliffe|
A mysterious evil is at work on Gallifrey. The President of the Time Lords has been assassinated and The Doctor caught red-handed. An inexorable master plan has been set in motion. There can be no escape. In order to prove his innocence The Doctor must pursue his enemy into the Matrix, a dream-like repository of knowledge formed from the minds of dead Time Lords.
However, he quickly discovers that in the Matrix the real assassin rules and behind this enemy lurks the even more deadlier menace of his old adversary – The Master.