When young Lila Dryden is found standing over the murdered body of her fiancé with a bloody dagger in her hand, her aunt, Lady Sybil Dryden, calls upon Miss Silver to investigate the situation. The murder weapon comes from the valuable collection of ivories which was owned by the murder victim, Sir Henry Whitall, a collection usually kept in a securely locked cabinet. Although Lila’s presence at the scene of the murder is incriminating, she insists that she was sleepwalking. Her former lover, Bill Waring, had returned and contacted her only that afternoon and is also held suspect. But because Sir Herbert was such a mean-spirited man, his entire staff and circle of acquaintances all had strong motives for wishing him dead. Miss Silver uncovers these motives with her particular brand of patience and rationality, untangling a web of mismatched love affairs, envy, and deceit.