The Doctor and Adric learn from the wizened Keeper of Traken that a great evil has come to his planet in the form of a Melkur - a calcified statue. The Keeper of Traken is nearing the end of his reign and seeks the Doctor's help in preventing the evil from taking control of the bioelectronic source that is the keystone of the Traken Union's civilisation.
| Writing | Johnny Byrne | Writer |
| Directing | John Black | Director |
| Production | John Nathan-Turner | Producer |
| Sound | Roger Limb | Original Music Composer |
| Production | Barry Letts | Executive Producer |
| Writing | Christopher H. Bidmead | Script Editor |
| Costume & Make-Up | Amy Roberts | Costume Design |
| Art | Tony Burrough | Production Design |
| Costume & Make-Up | Norma Hill | Makeup Artist |
| Production | Alan Wareing | Production Assistant |
| Camera | Alec Wheal | Camera Operator |
| Crew | Dick Mills | Special Sound Effects |
| Lighting | Don Babbage | Lighting Director |
| Sound | John Holmes | Sound |
| Sound | Alan Fogg | Sound |
| Visual Effects | Dave Chapman | Visual Effects |
| Editing | Rod Waldron | Editor |
| Visual Effects | Peter Logan | Visual Effects |
