The Guilby-Lacourts form a typical family of our time. Between a father, stepmother, little sister, brother, half-sister, and even a half-uncle, they sometimes have difficulty knowing who's who. 
One evening, they learn of the death of a grandfather with whom they'd cut off all contact years ago. Inevitably doomed to be stuck with each other during a long journey so they can go to his funeral, they must quickly adapt to the concept of "living together" in the cramped space of the family car. For better and for worse!