It is the early 1960s, and in a staid suburb fifteen miles south of London, Paul, nineteen, home from university for the holidays, is urged by his mother to join the tennis club. At the mixed doubles tournament he is partnered with Mrs. Susan Macleod: she's twice his age, and the married mother of two nearly grown-up daughters. Soon Paul and Susan embark on an unconventional affair, despite the disapproval of Paul's parents and the seething resentment of Susan's husband, who can't quite play along with the ruse that Paul is merely a surrogate son and family friend.