A killer called 'The Dark Man' commits double murder. This is witnessed by the young aspiring actress Molly Lester. The Dark Man tries everything to put Molly out of the way. Detective Inspector Viner of Scotland Yard investigates the murders.

Edward Underdown
as Detective Inspector Viner

Maxwell Reed
as The Dark Man

Natasha Parry
as Molly

William Hartnell
as Superintendent of Police

Barbara Murray
as Carol Burns

Robert Long
as Charles Burns

Cyril Smith
as Samuel Denny

Leonard White
as Detective Sergeant Evans

Ernest Haines
as Mostyn
CinemaSerf
Poor old "Molly" (Natasha Parry) has the misfortune to witness the eponymous character commit double murder. He knows she knows, and she knows he knows that she does, and so now he (Maxwell Reed) is determined to shut her up before she can tell pursuing police inspector "Vine" (Edward Underdown) and...