After being nearly killed by both a hired hit man and her former secretary, Agatha Raisin could use some low-key cases. So when Robert Smedley walks through the door of her detective agency, determined to prove that his wife is cheating on him, Raisin Investigations immediately offers to help. Unfortunately for Agatha, Mabel Smedley appears to be the perfect wife: young, pretty, and a regular volunteer at church.
But just as Agatha is ready to give up, Smedley is poisoned with weed killer, leaving Mabel, the prime suspect, poised to inherit a fortune. With no one left to pay her, Agatha has to drop the investigation - that is, until her old friend Sir Charles Fraith turns up again to rekindle her curiosity in the case.