David Bonner, John Heard is a college student who is dating a girlfriend and is secretly sleeping with a woman named Shelly, Beverly D'Angelo. Shelly arrives in his dorm room wearing only a towel and declares she will stay only until he finishes with his girlfriend, but the encounter lasts much longer. Afterward, David quietly thanks his friend Elgin by setting him up with Shelly.
Elgin Smith, [William Katt] first encounters Caroline Hedges, [Susan Dey] during a campus meal. Working as a busboy in the cafeteria, he spills tea on her and her book, but she still leaves her dormitory name on a scrap of paper. He brings her a fresh copy of the book and later asks her to coffee. Caroline hints at another boyfriend, but Elgin is smitten and eventually joins a class she is taking, three weeks after it started. Caroline reveals that her father is dead, and they go on their first real date to the symphony.
Caroline, [Susan Dey] then introduces Elgin to John March, [Robert Loggia], who is already married. She is unsettled by the meeting and asks to spend a night with Elgin so she won’t be alone. They begin to have sex, but they are interrupted by David, who says that Elgin is late for work. Elgin hurries to his job, and David convinces Caroline to ride back to her dorm on his motorcycle. Elgin spots them together and fights David in a jealous rage. Caroline tells him she is not interested in David. Elgin feels relief but is later fired for being late to work.
David and Caroline watch Elgin play a game of soccer; Elgin and Caroline resume their affair, and he asks about John, who worked with her father as a lawyer and whom she has known all her life. He grows jealous when he learns she slept with John, but Caroline becomes angry at the jealousy. Elgin grows nervous when he cannot reach her, but finds a note inviting him to join her, alone, at her family’s estate. He goes, and Caroline leads him to the past, including a childhood playhouse where her father committed suicide. The phone rings, revealing that John wants her back, and they cannot continue seeing each other. Elgin leaves on his motorcycle, while Caroline tells him goodbye and he is left alone.
Back at school, Elgin returns to his dorm to find Shelly waiting at his door. Shelly declares her love for David, but he does not reciprocate. Elgin declines another chance for sex.
Elgin runs into Caroline as she says goodbye to John, confessing that she is with John and their affair is over. Drunk, Elgin again finds Shelly at his door and agrees to be with her, but accidentally calls her Caroline mid-tryst. He attends Caroline’s class, but leaves when she does not appear. He visits John at his office to ask if his intentions are honorable. John mentions his shaky marriage but emphasizes that his children matter and does not know if he can divorce. Caroline shows up in Elgin’s room in the middle of the night, they sleep together, and she brings him breakfast in the morning. John decides not to pursue a divorce, leaving Elgin feeling like second best. The relationship ends, and Caroline departs on a train, while Elgin returns to his solitary soccer habit.