In a snowy wasteland, Vasor, an unscrupulous trapper, imprisons the travellers in a frozen cavern inside a mountain. There they find one of the keys frozen in a block of ice.
| Name | Type | Role | |
|---|---|---|---|
| Terry Nation | Writer | ||
| Alan James | Guest Star | ||
| Katherine Schofield | Guest Star | ||
| Peter Stenson | Guest Star | ||
| Robin Phillips | Guest Star | ||
| Anthony Verner | Guest Star | ||
| Michael Allaby | Guest Star | ||
| Francis de Wolff | Guest Star | ||
| John Gorrie | Director |