On board a vast spacecraft, the Doctor meets the alien captain who demands the return of the three ambassadors sent to Earth or he will destroy the world.
| Name | Type | Role | |
|---|---|---|---|
| David Whitaker | Writer | ||
| Malcolm Hulke | Writer | ||
| Peter Noel Cook | Guest Star | ||
| Carl Conway | Guest Star | ||
| Joanna Ross | Guest Star | ||
| Michael Ferguson | Director |