On a flight from London to Boston, Ted Severson meets a stunning girl named Lily Kitner. Over martinis, the two strangers play a game in which they reveal minute details about their lives. But what begins as a joke between Ted and Lily takes a serious turn when Ted half-seriously admits that he wants to kill his wife. He's genuinely surprised when Lily tells him she'd love to help him kill her. Back in Boston, Ted and Lily develop an unusual relationship and talk about ways Ted could end his marriage. However, Lily has a dark past she hasn't shared with Ted. Ted begins to fall for Lily, and meanwhile, he grows increasingly concerned that there are any holes in their plan that could catch them both out. Suddenly, they are both caught in a bloody game of cat and mouse, from which neither will likely survive if all is said and done.