Graham and Joan Bendix have apparently succeeded in making that eighth wonder of the modern world, a happy marriage. And into the middle of it there drops, like a clap of thunder, a box of chocolates. Joan Bendix is killed by a poisoned box of liqueur chocolates that cannot have been intended for her to eat. The police investigation rapidly reaches a dead end. Chief Inspector Moresby calls on Roger Sheringham and his Crimes Circle – six amateur but intrepid detectives – to consider the case. The evidence is laid before the Circle and the members take it in turn to offer a solution. Each is more convincing than the last, slowly filling in the pieces of the puzzle, until the dazzling conclusion.