Katherine, heading for her senior year in high school, finds herself strongly attracted to Michael, a friend's friend, after a party. As their relationship unfolds, the issue of sex comes up early on, more as an emotional and health issue than as a moral one. Both of them are aware that physical intimacy is both common and complicating. Michael has been sexually active, Katherine hasn't. Their relationship progresses slowly; they are accompanied on various meetings by her friend, Erica, a grounded, practical, wit who has known Katherine all her life, and Michael's friend, Artie, who, with Erica's help, explores and acknowledges some uncertainty about his own sexual orientation.

When they do, by mutual consent, have sex on a ski weekend with Michael's sister, they are sure it seals a love that will be "forever." However, separated for the summer by work that takes them to two different states, Katherine finds herself aware of the limitations of the relationship and ultimately attracted to a tennis instructor, older, more experienced, and interesting in new ways. She takes responsibility for breaking the news to Michael when he comes on a surprise visit and, the summer over, recognizes the loss as a stage in movement toward more complex, probably more satisfying relationships in the future.