David Hurst (Campbell Scott) is a mild-mannered dentist who shares a practice with his wife, Dana (Hope Davis). Concerned about Dana's recent sullen moods, David begins to suspect that she is cheating on him. As David becomes deeply unsettled by the possibility of Dana's infidelity, he begins having extended conversations with Slater (Denis Leary), a surly patient who dispenses plenty of blunt advice. Can Dana and David reconcile and save their marriage, or are they destined to separate?