Puzzles of th Black Widowers - Isaac Asimov

Each month the Black Widowers, an urbane club of cerebral adventurers, meet at the Milano Restaurant for dinner. And each month a single guest is invited and subjected to a genial but intense grilling on the meaning of his existence. Inevitably the guest confides some puzzling question or strange occurrence in his life - the inexplicable disappearance of a good luck charm, for instance, or how a four-leaf clover can identify a traitor - tantalizing conundrums that the great Holmes himself would have enjoyed solving.

When the Black Widowers are stumped (as invariably happens), they turn to their faithful waiter Henry, who serves up perfectly grilled salmon and devilishly clever answers with equal aplomb.