Patrick Holt
— Inspector Gregory
Emrys Jones
— Howard Rogers
Honor Blackman
— Ann Rogers
Bruce Beeby
— Det. Sgt Conway
John Horsley
— Mr. Fisher
Robert Perceval
— Bank Manager
Wally Patch
— Barman
Frank Pettitt
— Fred (as Frank Pettit)
Benedicta Leigh
— Policewoman Scott
Peter Glaze
— Station Booking Clerk
Vi Stevens
— Landlady
Howard Greene
— River Police Sergeant
Raymond Smith
— River Police Constable
Lawrence James
— Uniformed Constable
Reginald Hearne
— Doctor (as Reggie Hearne)
Barry Linehan
— Forensic Chemist
Gerry Duggan
— Norman Cole
Colin Rix
— Plain Clothes Detective
Bill Mills
— Photographer
Pat Shaw
— Uniformed Policewoman
John Tatham
— PC Barrow (uncredited)