The Devil Plays (1931) is a whodunit awash in people that look alike and, to some extent, act alike. Someone is poisoned at an overnight dinner party, a detective fiction writer helps the prickly police while politely lusting after one of his fellow suspects, there’s money for a tea room, and, oh, I don’t care. That’s how I felt at the end.
At least it’s not too long. But that’s hardly an excuse for sitting through it.