Charles Cokley (Cotten) comes to visit his sister Emma and her family.

But his niece Charlie (Wright) begins to suspect that her 'Uncle Charlie' is really the crazed 'Merry Widow Killer'.

Could her slightly offbeat uncle really be a cold blooded murderer, or does she just have an overactive imagination?

And if her suspicions are valid, will the young girl survive for long?

Wright is dead on as Uncle Charlie's young niece - lending the role a brisk, decidedly modern feel - while Cotten is wonderfully sinister as the horrible killer who will do anything to hide his guilt.

Best scene: that memorable "struggle on a train" finale.

Hitch does a great job of taking an intelligent and clean cut atmosphere and giving it a truly realistic hue of malice and suspicion.

One of Hitchcock's personal favorites from among his own superlative menagerie - and it's easy to see why.

Definitive viewing.