The Snorkel

Although the police have termed her mother's death by gas a suicide, a teenage girl (Mandy Miller) believes her step-father (Peter VanEyck) murdered her.

Hammer may be best known for their horror films, but they made some pretty fine thrillers and murder mysteries, too, as this film attests. Helmed by Guy Green (who made his name under David Lean) and written by Hammer's Jimmy Sangster, this is just pure genius beginning to end.

From the opening scene, we know how the killer does his work... but then we watch and see if his teenage stepdaughter can find out. Blaming someone for murder is one thing, but finding solid proof is something else entirely.