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.
| Directing | Michael Hayes | Director |
| Writing | Bob Baker | Writer |
| Writing | Dave Martin | Writer |
| Production | Graham Williams | Producer |
| Writing | Anthony Read | Script Editor |
| Writing | Douglas Adams | Script Editor |
| Production | David Maloney | Producer |
| Sound | Dudley Simpson | Original Music Composer |
