The Doctor and UNIT investigate a deadly infection lurking underneath the Welsh mining town of Llanfairfach. It's an adventure that will change Jo Grant's life forever...
| Directing | Michael E. Briant | Director |
| Writing | Robert Sloman | Writer |
| Editing | Alastair Mackay | Editor |
| Crew | Terry Walsh | Stunt Coordinator |
| Production | John Harris | Production Assistant |
| Crew | Dick Mills | Special Sound Effects |
| Lighting | Mike Jefferies | Lighting Director |
| Art | John Burrowes | Production Design |
| Sound | Richard Chubb | Sound |
| Camera | Ken Lowe | Camera Operator |
| Sound | Dudley Simpson | Original Music Composer |
| Camera | Bill Matthews | Camera Operator |
| Writing | Terrance Dicks | Script Editor |
| Costume & Make-Up | Barbara Kidd | Costume Design |
| Sound | Simon Wilson | Sound |
| Production | Michael McDermott | Production Assistant |
| Costume & Make-Up | Ann Rayment | Makeup Artist |
| Production | Barry Letts | Producer |
| Visual Effects | Ron Oates | Visual Effects Designer |
