Jo attempts to rescue the Doctor who is being held prisoner by the Master and Trenchard. The Master plans to summon the Sea Devils from beneath the waves.
| Name | Type | Role | |
|---|---|---|---|
| Malcolm Hulke | Writer | ||
| Christopher Wray | Guest Star | ||
| Clive Morton | Guest Star | ||
| Stanley McGeagh | Guest Star | ||
| Michael E. Briant | Director |