Someone clever has done it--but whom? Gather everyone, all in a room Who committed the crime Will admit it in time Though it's never the one you assume.
Whodunnits and mysteries often employ a penultimate scene where the detective gathers all the suspects together. Here Nick and Nora Charles hold a dinner party in The Thin Man (W. S. Van Dyke; 1934). David Cairns came up with the title, and he's also guilty of suggesting the scene.