On Christmas Eve, commercial artist Molly Gilmore and architectural engineer Frank Raftis are both separately doing last-minute Christmas shopping in
Manhattan. Frank meets his colleague Ed for drinks, and Ed tells Frank that he is getting divorced. Molly sees her friend Isabelle, who is married but plans to spend Christmas with another man. Molly also visits her sick father. Later that day, at the counter in a hectic
bookstore, Frank and Molly mix up their packages, so on Christmas Day, Molly's husband Brian and Frank's wife Ann both open the book meant for the other. Three months later, Frank and Molly, who commute to Manhattan from adjacent stops on the
Metro-North Hudson Line, run into each other on the morning train. They struggle to place each other, but Frank soon remembers and reminds her of the confusion over the books. Later that day, Frank's boss asks him to take a job in Houston, while Molly visits her father in hospital. Molly tells Isabelle about Frank; Frank tells Ed about Molly. That evening, Frank waits for Molly at
Grand Central Terminal. They talk and agree to meet on the morning train later that week. Against their better judgement, Frank and Molly grow closer. They see more of each other until one afternoon, Frank takes Molly to Ed's apartment. They begin to make love, but Molly cannot continue it. They agree that they must stop seeing each other. When Molly returns home, Brian gives her the news that her father has died. At the funeral, she has a panic attack. Convalescing, she tells Isabelle that it is not grief for her father from which she is suffering, but the loss of Frank. Meanwhile, Frank agrees to take the job in Houston. He tells Ann about the job change, but she inquires about the sudden difficulties of their marriage. When he confesses about his relationship with Molly, Ann is taken aback and decides to leave, taking the children to Denver to live with her mother. On the night when he is due to leave, Frank calls Molly at home. Frank asks to see her before he goes, but as Brian stands listening, she ends the call. Unable to resist, she tells Brian that she must see Frank one more time and rushes to her car. Driving fast in the pouring rain, she nearly collides with a train at a crossing and misses her chance. Meanwhile, Frank tries to call her again but her husband answers the phone and says that she does not want to talk to Frank. The following Christmas season, Frank meets Ed for lunch and tells him that he and Ann are now separated; she living in Denver and he continuing to live in Houston. Frank is planning to sell the
Dobbs Ferry home and return to Texas. Molly meets Isabelle, and it is clear from their conversation that her marriage to Brian has failed too. Frank makes a stop at the bookstore at which he and Molly first met. Coincidentally, Molly is there at the same time. They talk but, uncertain how things now stand between them, go their separate ways. Walking away from the store, Frank stops, turns and runs after her. A short time later on a crowded train out of Grand Central, he finds her again. They embrace. ==Cast==