On the lush planet Tigella, two opposing factions are divided over the usage of the Dodecahedron, an ancient and powerful artefact which provides the entire planet's energy. The Doctor is summoned to arbitrate the conflict, but the power-crazed Meglos intercepts the call and impersonates him in order to steal the Dodecahedron.
| Production | John Nathan-Turner | Producer |
| Directing | Terence Dudley | Director |
| Writing | John Flanagan | Writer |
| Production | Barry Letts | Executive Producer |
| Writing | Andrew McCulloch | Writer |
| Writing | Christopher H. Bidmead | Script Editor |
| Sound | Paddy Kingsland | Original Music Composer |
| Sound | Peter Howell | Original Music Composer |
| Costume & Make-Up | June Hudson | Costume Design |
| Art | Philip Lindley | Production Design |
| Costume & Make-Up | Cecile Hay-Arthur | Makeup Artist |
| Production | Marilyn Gold | Production Assistant |
| Camera | Alec Wheal | Camera Operator |
| Crew | Dick Mills | Special Sound Effects |
| Lighting | Bert Postlethwaite | Lighting Director |
| Sound | John Holmes | Sound |
| Editing | Ian Williams | Editor |
| Editing | Sam Upton | Editor |
| Visual Effects | Steven Drewett | Visual Effects |
