The coroner's verdict: suicide, after beautiful heiress Rosemary Barton dies from drinking a cyanide-laced glass of champagne at her own birthday party. Her husband George doesn't believe it, based on two anonymous letters that suggest murder. But who has a motive? Rosemary's lover or the lover's spurned wife, her penniless sister, or even George or his secretary? One year after her death, six gather for dinner in remembrance. The plan is to trap the killer, but instead, death strikes again!