Clément, a young entrepreneur, is a happy father: married to the beautiful Alex, he is also the happy father of "Petit-Bonheur", his son. Despite his 30 years, he can't live without his father, Paul, a musician and widower, with whom he has a very close relationship. In addition to this exclusive relationship, the latter also takes care of his grandson on a regular basis. Two points which are not without provoking a certain jealousy in Alex. One day, "Petit-Bonheur", under Paul's care, falls down a staircase. At the hospital, where the child undergoes X-rays, Clément can't stand the wait for the exams and reprimands his father harshly. After this incident, the news is fortunately good: "Petit-Bonheur" has nothing serious and finds with joy the arms of his parents. Clément then realizes that his father has disappeared.