Antoine Doinel is 26 and happily married to Christine. Whilst his wife gives violin lessons, Antoine works for a florist, dyeing flowers. However, he soon loses interest in this job and decides to go for an interview with an American construction company. To his surprise, he is offered a job, operating radio-controlled boats in a scale-model of a harbour. Here, he meets Kyoko, an attractive Japanese young woman, who belongs to the entourage of an important customer. In spite of the fact that his wife has just given birth, Antoine starts to have an affair with Kyoko. When she learns the truth, Christine is furious. It looks as if her marriage with Antoine might well be over.