The movie opens with Eve Gill (Jane Wyman) and Jonathan Cooper (Richard Todd) in a car, clearly worried that the police are after them. Jonathan explains to Eve what's happened: he's been having an affair with famous stage actress Charlotte Inwood (Marlene Dietrich), and when her husband abused her and she accidentally killed him while defending herself, she turned to Jonathan for help - and he may now be suspected of the murder. Eve is infatuated with Jonathan, despite his affair with Charlotte. She knows she's being used, and says to Jonathan "I wish I'd taken courses in playing second fiddle." She takes him to her father's seaside home, in the hope of hiding Jonathan on her father's boat. It was when we met her father (Alastair Sim - most famous as Scrooge in "A Christmas Carol") that I completely fell for the movie: her father is a quick-witted old smuggler who clearly loves his innocent young daughter and understands her personal foibles better than she does. This kind of writing has always been one of Hitchcock's greatest strengths: he never has to spend time on exposition to tell you about people because their characters shine through in their speech and behaviour. So much so that two minutes with his characters is better than half an hour of blundering fluff provided by the vast majority of Hollywood screenwriters. The scene between Wyman and Sim would have made the whole movie worth while by itself, but there's plenty more fun to be had.
Eve concludes that her best course of action is to put her acting skills to work to try to expose Charlotte Inwood to take the heat off Jonathan. There are plenty of twists and turns along the way, including a handsome police detective (Michael Wilding, who's a dead ringer for Alan Cumming) and a black-mailing housekeeper. I don't like Dietrich and I really don't like Dietrich doing staged musical numbers. I wasn't keen on the big twist at the end. And yet the quality of the writing made this wonderful fun to watch.