Philosopher and amateur sleuth Isabel Dalhousie has an unstinting commitment to her principles. Sticking to her promises has always been one of them. Then Isabel runs into an old classmate facing marital and financial troubles, who reveals a secret about a painting up for auction that becomes more and more difficult for Isabel to keep. In the meantime she comes across a revealing note accidentally put in the pocket of her son's jacket at daycare, and obviously intended for another classmate's parent. Thankfully, Isabel's devoted husband, Jamie, is there to help our heroine navigate her competing moral obligations.