On his way home on the train one night, Syohei, an accountant stuck in the midst of the midlife doldrums, sees a woman staring out a second floor window and looking as lonely and melancholy as he feels. Intrigued he looks for her each night from the train, and one night, impulsively gets off the train at her stop. It turns out her window belongs to a social dancing studio, and she is an instructor there. Syohei signs up for lessons, and soon he is spending so much time at the studio that his wife hires a detective out of fear that he is having an affair. He is having an affair all right, but with the mambo and the cha cha cha and the liberation that dance brings him.