MAY CONTAIN SPOILERS.
That's an underrated Hitchcock movie that contains, as most of his films, a lot of symbolism (I just want to mention this but I don't want to go into it because usually all these symbols are not something a viewer notices himself they require literature!). But it's also, apart from some weaknesses, a great piece of suspense. A lot of hiding and dressing up and pretending to be someone else
I like that.
The various characters and the actors who played them are also worth mentioning. Marlene Dietrich is really revealed as a bad actress as soon as she stops playing herself. Interestingly, this happens only in a flashback which later turns out to be a lie. The role of the arrogant diva suits her perfectly. Jane Wyman does a great job as Eve Gill, and also as Doris, the housemaid she pretends to be. The most hilarious character in the film, giving it a touch of comedy, is Eve's father, who is played by Alastair Sim: a phlegmatic, clever old man with dramatic sense who constantly seems to understand and accept everything that happens around him.
Not one of Hitchcock's most outstanding thrillers, but still: a Hitchcock.