Lord Peter investigates his sister's flirtation with Bolshevism and a romantic involvement with a Communist activist.
| Name | Type | Role | |
|---|---|---|---|
| Dorothy L. Sayers | Writer | ||
| Anthony Steven | Writer | ||
| Kate O'Mara | Guest Star | ||
| Anne De Vigier | Guest Star | ||
| Frances Jeater | Guest Star | ||
| Richard Cornish | Guest Star | ||
| Lockwood West | Guest Star | ||
| David Hargreaves | Guest Star | ||
| André Maranne | Guest Star | ||
| Hugh David | Director |