When a married couple decides to move to France with their young daughter for a few months, they ask a distant cousin, Martin, to house sit and take care of their cat. At 40 years old, Martin has no kids, no wife, and no job. Despite Martin's brooding and strange demeanor, the family dismisses any doubts they have and leave the house in his care. Left to his own devices, Martin spends his days indoors chain-smoking, looking through their belongings, trying on their clothes, and moving the furniture around how he likes. Slowly, Martin becomes seduced by the idea of family life, treating the house as if it's his own. One day, the cat goes missing. Martin goes out searching for him and falls for Pachi, an attractive single mother. He brings her to the house and wins her over by posing as a divorcee who doesn't get to see his daughter because of his vindictive ex-wife. Before long, Pachi is bringing her young son over to the house, turning their casual fling into domestic bliss. As the imminent return of the real family gets closer and closer, Martin's pseudo-family begins to unravel.