Mel and Pex play cat and mouse with the lethal cleaner robots while the Doctor and the surviving Kangs learn all about Kroagnon the Great Architect.
| Name | Type | Role | |
|---|---|---|---|
| Stephen Wyatt | Writer | ||
| Brenda Bruce | Guest Star | ||
| Richard Briers | Guest Star | ||
| Elizabeth Spriggs | Guest Star | ||
| Judy Cornwell | Guest Star | ||
| Howard Cooke | Guest Star | ||
| Simon Coady | Guest Star | ||
| Catherine Cusack | Guest Star | ||
| Julie Brennon | Guest Star | ||
| Annabel Yuresha | Guest Star | ||
| Nicholas Mallett | Director |