Earth, 1964. Ian and Barbara are accidentally taken into Smithers' laboratory and, while the Doctor and Susan face a hazardous journey to reach them, they witness the deadly effects of DN6 first hand.
| Name | Type | Role | |
|---|---|---|---|
| Louis Marks | Writer | ||
| Alan Tilvern | Guest Star | ||
| Reginald Barratt | Guest Star | ||
| Rosemary Johnson | Guest Star | ||
| Fred Ferris | Guest Star | ||
| Douglas Camfield | Director | ||
| Mervyn Pinfield | Director |