Castle and Beckett investigate the murder of a woman found drowned in a bathtub of motor oil at a transient hotel. But when they uncover a dark secret about the woman's past, they must unravel a 20-year-old mystery with the help of a true crime journalist who may have been stalking the victim. Meanwhile, Beckett puts her poker face to the test as she squares off against Castle, with her money and pride at stake.