The Doctor arrives on Jaconda, once lush and green, to find it completely devastated by giant gastropods. Old legends about the planet's half-human/half-slugs weren't just myths after all. With or without help from the Doctor and his unpredictable mood swings, Lt. Lang is up for rescuing the twins, who are finally informed of the grand purpose they've been brought to Jaconda to accomplish.
| Name | Type | Role | |
|---|---|---|---|
| Anthony Steven | Writer | ||
| Gavin Conrad | Guest Star | ||
| Barry Stanton | Guest Star | ||
| Andrew Conrad | Guest Star | ||
| Oliver Smith | Guest Star | ||
| Maurice Denham | Guest Star | ||
| Roger Nott | Guest Star | ||
| John Wilson | Guest Star | ||
| Kevin R. McNally | Guest Star | ||
| Peter Moffatt | Director |