The elderly Mrs. Bransom (Whitty) is wealthy, controlling and cantankerous.

At her secluded estate out in the country, she runs a strict household, verbally abusing her submissive niece Olivia (Russell), and browbeating her servants Tottenham and Harrison.

But when the old woman meets sweet talking handyman Danny (Montgomery), she falls for his devilish charms - and how!

Soon, Danny has become Mrs. Bransom's "personal assistant" and close friend.

There's only one problem. Seems there's a psychotic killer on the loose who's been murdering helpless women in the nearby countryside.

One poor victim has been found strangled, and missing her head.

And Mrs. Bransom's niece Olivia fears Danny is the psycho the police are seeking.

After all, what could he be hiding in that strange, hat-shaped box he keeps locked under his bed? Why is he so protective of it, not allowing anyone near it?

Montgomery is a revelation as the murderous Danny, delivering a smooth performance filled with nuanced glimpses of conscious - and subconscious - evil.

(Just check out his final breakdown scene: amazing.)

Grande dame Whitty, who appeared in a couple of early Hitchcock films, provides just the right blend of frothy disagreeableness here.

And there's some excellent tension-filled scenes between Russell and Montgomery, not to mention a knockout ending which doesn't pull any punches.

A must see. Remade in 1964.