The HQ is destroyed by the web and everyone is captured by Yetis. The traitor is revealed and all seems lost as the Doctor submits himself to the Great Intelligence's mind drain.
| Name | Type | Role | |
|---|---|---|---|
| Mervyn Haisman, Henry Lincoln | Writer | ||
| Jon Rollason | Guest Star | ||
| Roger Jacobs | Guest Star | ||
| Douglas Camfield | Director |