A highly intelligent spider from Metebelius III arrives on Earth in search of the powerful crystal. When it is stolen from his laboratory, the Doctor leads the chase over land, water and air to recover it.
| Name | Type | Role | |
|---|---|---|---|
| Barry Letts, Robert Sloman | Writer | ||
| Chubby Oates | Guest Star | ||
| Michael Pinder | Guest Star | ||
| Barry Letts | Director |