Scotland, the near future. Something is smashing oil rigs off the Scottish coast, and UNIT have been called in to investigate. The aliens responsible, the Zygons, try to kill the Doctor and Sarah Jane, then attempt to recover their signal device using their ability to mimic human beings.
| Name | Type | Role | |
|---|---|---|---|
| Robert Banks Stewart | Writer | ||
| Tony Sibbald | Guest Star | ||
| Ronald Gough | Guest Star | ||
| Bernard G. High | Guest Star | ||
| John Woodnutt | Guest Star | ||
| Lillias Walker | Guest Star | ||
| Douglas Camfield | Director |