Desperate Margaretta Seymore is with child - and her husband is receiving poisoned pen letters which imply that her condition is the result of an affair with the notorious actor Fletcher Cavendish. Margaretta asks the sleuthing Rosalind Thorne to find out who is behind the scurrilous letters. But before she can make any progress, Cavendish is found dead, stabbed through the heart. Suddenly, Rosalind is plunged into the middle of one of the most sensational murder trials London has ever seen...