Edward and Connie Sumner, who live in a commuter suburb of New York City with their adolescent son Charlie, have a relatively happy eleven year marriage, although they both lead hectic day-to-day upper middle class lives away from each other that take away from their ability to spend time together. They decided to move from the city following Charlie's arrival into their lives. One day in the city, Connie meets younger Frenchman Paul Martel, a used book seller, by literally running into him. Although not looking for anything outside of her marriage, Connie finds that she can't stop thinking about Paul, and despite she looking for and receiving validation of the strength of her marriage to and from Edward, she and Paul embark on a passionate affair punctuated with light S&M, the affair about which she feels both constant excitement and guilt. Over time, Edward begins to find clues both that all is not all right in their marriage and that Connie's stories about her day-to-day goings-on do not add up to the truth. If Edward does find out about Connie's affair, Paul who Connie had previously mentioned to him as the white knight who helped her during a crisis, the questions become what Edward will do, both about Paul and about his marriage to Connie, he who has implied through previous action with someone much less important in his life that loyalty is paramount to him, and what the consequences of any of his actions will be.