While the Doctor plans a holiday to Metebelis Three, Jo and the Brigadier are intrigued by a mysterious death at a coal mine in Llanfairfach, which is being blamed on local company Global Chemicals.
| Name | Type | Role | |
|---|---|---|---|
| Robert Sloman, Barry Letts | Writer | ||
| Mostyn Evans | Guest Star | ||
| Ben Howard | Guest Star | ||
| Tony Adams | Guest Star | ||
| Ray Handy | Guest Star | ||
| Talfryn Thomas | Guest Star | ||
| Michael E. Briant | Director |