UNIT are summoned to Wenley Moor research station which is experiencing mysterious power losses. In the nearby caves, one of the staff has been killed and another sent insane.
| Name | Type | Role | |
|---|---|---|---|
| Malcolm Hulke | Writer | ||
| John Newman | Guest Star | ||
| Roy Branigan | Guest Star | ||
| Ian Cunningham | Guest Star | ||
| Fulton Mackay | Guest Star | ||
| Timothy Combe | Director |