Landing at the South Pole, the travellers find that Earth's twin planet is disrupting a space mission. The Doctor predicts that they will soon receive visitors from the new planet.
| Name | Type | Role | |
|---|---|---|---|
| Kit Pedler | Writer | ||
| Dudley Jones | Guest Star | ||
| Christopher Matthews | Guest Star | ||
| Robert Beatty | Guest Star | ||
| Steve Plytas | Guest Star | ||
| John Brandon | Guest Star | ||
| Shane Sheldon | Guest Star | ||
| Alan White | Guest Star | ||
| Earl Cameron | Guest Star | ||
| David Dodimead | Guest Star | ||
| Derek Martinus | Director |