In the underground city, the Doctor and the Master confront the guardian of the Doomsday Weapon. The miners make their last move to force the colonists to leave the planet.
| Name | Type | Role | |
|---|---|---|---|
| Malcolm Hulke | Writer | ||
| Norman Atkyns | Guest Star | ||
| Roy Heymann | Guest Star | ||
| Michael E. Briant | Director |