The Doctor investigates Rossini's International Circus. The Master, meanwhile, has assumed control at the plastics factory and is manufacturing new lines of living plastics.
| Name | Type | Role | |
|---|---|---|---|
| Robert Holmes | Writer | ||
| John Baskcomb | Guest Star | ||
| Stephen Jack | Guest Star | ||
| Barbara Leake | Guest Star | ||
| Harry Towb | Guest Star | ||
| Barry Letts | Director |