An energy drain traps the Third Doctor and Sarah Jane Smith on the planet Exxilon with its hostile natives, causing the travellers to make an uneasy alliance with a Marine Space Corps expedition and a squadron of Daleks. The key to escape for all of them lies at the heart of a powerful and mysterious lost city, but only after a series of deadly traps.
| Writing | Terry Nation | Writer |
| Directing | Michael E. Briant | Director |
| Editing | Bob Rymer | Editor |
| Art | Colin Green | Production Design |
| Production | Barry Letts | Producer |
| Costume & Make-Up | L. Rowland-Warne | Costume Design |
| Visual Effects | Jim Ward | Visual Effects |
| Sound | Richard Chubb | Sound |
| Sound | Dick Mills | Sound |
