I know what you're thinking. You're thinking, "How could a movie with Cary Grant and Audrey Hepburn be overlooked?" I agree, but maybe there's somebody reading this who hasn't see the movie. It's a lot of fun.
To begin with you have the leads, Audrey Hepburn and Cary Grant. Hepburn is about to divorce her husband, and Grant is the suave, mysterious stranger. Hepburn returns to Paris to find her husband murdered and herself mixed up in a plot to recover $250,000 in stolen Nazi gold. Three men are after it, and they believe Hepburn has it. They are bad guys, indeed (George Kennedy, James Coburn, Ned Glass). Somehow Grant is mixed up in it, too, and he's clearly not to be trusted. He's very inventive, however, and every time Hepburn discovers that he's not who he says he is, he very plausibly claims to be someone else. This happens often. The CIA, represented by Walter Matthau, is also in on the game.
Hepburn doesn't have the stolen gold and has no idea where it is. That doesn't matter to the bad guys. They're going to keep after her. And they they start getting killed. Is someone else is in on the game, too? And who the hell is Cary Grant, really?
There's plenty of scenery, witty banter, action, and mystery here. Plus music by Henry Mancini. If you're looking for topnotch light entertainment, this is it.
Peter Stone, who wrote the screenplay, also published the novel version. It's a Gold Medal book, and I read it 50 years or so ago. I'm pretty sure I liked it.