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
The Doctor
Mary Tamm
Romana
John Leeson
K-9 (voice)
John Woodvine
Marshal
Lalla Ward
Princess Astra
Davyd Harries
Shapp
Ian Saynor
Merak
Ian Liston
'Hero'
