The elderly Mrs. Gentle lives in a large seaside castle near the sleepy Scottish village of Lochdubh. She wears lavender-colored clothes, and her white hair is delicately colored with a matching tinge. She is kind and solicitous of her neighbors. She has generously agreed to donate a considerable sum of money to the local church. She wears charming, old-fashioned, violet-trimmed bonnets in the summer and lavender felt hats in the winter. Everyone in Lochdubh adores her.

Everyone save the redheaded Constable Hamish Macbeth, who sees through all the lavender - especially when Mrs. Gentle's meddling leads to the possible closing of his beloved police station. To combat her sly machinations, the unrepentant bachelor proposes to her comely blonde maid, Ayesha. Macbeth has had brushes with the altar before, but this time he's serious: He knows his superiors won't terminate the station of a married man.

But murder has a way of making the best laid plans gang aft agley. When Mrs. Gentle turns up dead, the town is shocked and outraged - though Macbeth privately thinks she angered more people than she pleased. While Detective Chief Inspector Blair suspects members of the victim's family, more people die ... and Macbeth begins to discover the shocking truth behind Mrs. Gentle's all-too-gentle facade.