The TARDIS crew arrives on Earth in the 26th Century in a cave system where a military force is investigating the disappearance of a palaentological expedition.
| Name | Type | Role | |
|---|---|---|---|
| Eric Saward | Writer | ||
| Anne Clements | Guest Star | First Trooper | |
| June Bland | Guest Star | ||
| Ann Holloway | Guest Star | Mitchell | |
| Mark Hardy | Guest Star | ||
| Beryl Reid | Guest Star | ||
| Alec Sabin | Guest Star | ||
| David Banks | Guest Star | ||
| James Warwick | Guest Star | ||
| Clare Clifford | Guest Star | ||
| Peter Grimwade | Director |