An obstetrician So-young has been happily married to an university professor Ji-seok. One day, however, So-young realizes that Ji-seok has an affair with one of his students Su-ji when she pays a visit to his office. In despair, So-young approaches to Su-ji and takes her yoga class to spy on her. Without knowing So-young’s true intention, Su-ji begins to befriend her. As Su-ji’s affection toward So-young grows, So-young’s rage turns into sympathy. In confusion, So-young decides to make a choice between Su-ji, who became a close friend of her, and her unfaithful husband Ji-seok.