Incredibly droll, this Graham Greene-scripted black comedy offers a can't miss premise: In pre-Castro Cuba (though shot shortly after the revolution), Alec Guinness sells vacuum cleaners to support a daughter with expensive tastes. He's soon made an offer he can't refuse: Become a spy for the British government to earn more cash. When he doesn't encounter much in the way of secrets, he makes them up. Soon, one of his made-up contacts somehow turns out to be a real person, with disastrous results. Crammed full of subtle sight gags and bone-dry one-liners, it's an underseen treat.