The final segment of the Key to Time is at the heart of a devastating war between neighbouring planets Atrios and Zeos. The Fourth Doctor discovers that a sinister entity is manipulating events and the cost of obtaining the final segment may be more personal than he imagined.

Tom Baker
as The Doctor

Mary Tamm
as Romana

John Leeson
as K-9 (voice)

John Woodvine
as Marshal

Lalla Ward
as Princess Astra

Davyd Harries
as Shapp

Ian Saynor
as Merak

Ian Liston
as 'Hero'

Susan Skipper
as 'Heroine'

John Cannon
as Guard
CinemaSerf
This final, six-part, instalment of the "Key to Time" series splits quite neatly into two stories, really. The first sees our travelling Time Lord (Tom Baker) and his colleague "Romana" (Mary Tamm) arrive on the planet of "Atrios" right in the middle of their war with the neighbouring "Zeos". Thus f...