The Doctor and Romana learn the second segment of the Key to Time is on the planet Calufrax. Yet they arrive on a planet called Zanak, which has been hollowed out and fitted with hyperspace engines, allowing its insane, half-robot Captain to materialise it around smaller planets and plunder their resources.
| Writing | Douglas Adams | Writer |
| Directing | Pennant Roberts | Director |
| Production | Graham Williams | Producer |
| Writing | Anthony Read | Script Editor |
| Sound | Dudley Simpson | Original Music Composer |
