Caught in a loveless marriage, Dr. John Winnington (Ronald Howard) can't stop himself from falling for his wife's (Mary Laura Wood) younger sister, Christine (Olga Edwardes). But when he suddenly becomes the prime suspect in his wife's tragic murder, John relies on his friend Eric (John Bentley) to clear his name. This classic murder mystery encourages viewers to evaluate all of the clues and guess the killer's identity.
| Actor | Role |
|---|---|
 Ronald HowardDr.John Winnington | Dr.John Winnington |
 Olga EdwardesChristine Shaw | Christine Shaw |
 John BentleyEric Blair | Eric Blair |
 Mary Laura WoodSophie Winnington | Sophie Winnington |
 Patrick BarrVincent Humphries | Vincent Humphries |
 Sheila BurrellAnnette | Annette |
 Russell NapierInspector Markham | Inspector Markham |
| MMary JonesMrs. Humphries | Mrs. Humphries |
| AAlan RobinsonSolicitor | Solicitor |
 Ian FlemingCoroner | Coroner |
 Tom GillTravel Agent Clerk | Travel Agent Clerk |
| TTucker McGuireAmerican Woman | American Woman |
| RRichard ShawLorry Driver | Lorry Driver |
| DDaniel WherryPadre | Padre |
 Bruce BeebySgt. Hawkins (uncredited) | Sgt. Hawkins (uncredited) |
| VVictor HarringtonCocktail Party Guest (uncredited) | Cocktail Party Guest (uncredited) |
| RRobin DowellBoy Patient (uncredited) | Boy Patient (uncredited) |