This is an old-fashioned caper movie, not that there's anything wrong with that when the movie's done right, as this one mostly is. The setting is 1960, which means that we don't have any high-tech glitz or complications. In fact, there are only two people involved in the Big Caper, Demi Moore and Michael Caine. Moore's not one of my favorites, but she does just fine, and Caine's low-key performance is so good that it seems almost effortless. That's not an easy thing to pull off.
Moore works for a diamond brokerage firm that seems to have all the diamonds in Britain. Caine is a janitor there. When Moore is passed over (again) for a well-deserved promotion and is about to be fired after suggesting an excellent idea that the firm has adopted, Caine proposes to her that the two of them steal enough diamonds to fill his thermos. Moore reluctantly goes along.
You know the drill. There are complications. There's a nice surprise about halfway through (well, it surprised me; you might not be so gullible). You know you want the criminals to succeed because the diamond brokers are such swine, but is it possible? The movie doesn't have any big action scenes, there are no explosions, and Demi Moore is fully clothed at all times. But there's plenty of entertainment if you like a good caper and don't mind a slower pace than is usually the case these days. And they use the "Pink Panther" theme music, too.