Apparently this was Alfred Hitchcocks last movie. It was pretty good, in a not 100% Hitchcock style..
It's quite different from the North by Northwest or 39 Steps scene atmosphere, although so dark (in the not B&W sense of the word).
There are lots of twists and turns and I like how the mood is set by the camera work and not by Hollywoodesque special effects.
In short: An old rich lady asks a fake psychic to find her only heir, her long lost nephew.
In the mean time, a miljonair and an archbishop get abducted by a mysterious lady in black who asks huge diamands as ransom.