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 , Mary Tamm , John Leeson , John Woodvine , Lalla Ward , Davyd Harries , Susan Skipper , John Cannon , Pat Gorman , William Squire
BBC
