When wealthy Lucille Ainsworth is found strangled on Hampstead Heath, Detective Inspector Marshall is put on the case.

Griffith Jones as Robert Ainsworth
Ursula Howells as Lucille Ainsworth
Honor Blackman as Sarah Hayward
Ewen Solon as Detective Inspector Marshall
Carl Bernard as Gilbert Morgan
Mary Jones as Nella Langford
Philip Gilbert as John Langford
John Van Eyssen as Clive Franklyn
Robert Raikes as Detective Sergeant Berry
Gordon Phillott as Rigby
Doris Yorke as Landlady
Vernon Smythe as Colonel Jarvis
Gerda Larsen as Blondi
Harry Ross as Bernard Goodman
Barry Steele as Barman
Edwin Richfield as Porter

Directed by Peter Graham Scott