With Zaroff's plan nearing completion, the Doctor and Ben realise the only way to save the world is to destroy Atlantis.
| Name | Type | Role | |
|---|---|---|---|
| Geoffrey Orme | Writer | ||
| Joseph Fürst | Guest Star | ||
| Tony Handy | Guest Star | ||
| P.G. Stephens | Guest Star | ||
| Graham Ashley | Guest Star | ||
| Paul Anil | Guest Star | ||
| Catherine Howe | Guest Star | ||
| Julia Smith | Director |