The parallel Inferno has broken through the Earth's crust, unleashing terrible seismic forces and dooming the planet. The Doctor hopes to return and save his world. But the bestial primords are closing in...
| Name | Type | Role | |
|---|---|---|---|
| Don Houghton | Writer | ||
| Derek Newark | Guest Star | ||
| Olaf Pooley | Guest Star | ||
| Keith James | Guest Star | ||
| Sheila Dunne | Guest Star | ||
| Christopher Benjamin | Guest Star | ||
| Philip Ryan | Guest Star | ||
| John Levene | Guest Star | ||
| Nicholas Courtney | Guest Star | ||
| Pat Gorman | Guest Star | ||
| Ian Fairbairn | Guest Star | ||
| Peter Thompson | Guest Star | ||
| Dave Carter | Guest Star | ||
| Douglas Camfield | Director | ||
| Barry Letts | Director |