The Martin family is shopping in a department store. Tiennot is responsible for looking after his little brother, Bébert, but he prefers to chase girls. On the train home, Tiennot leaves Bébert alone. On arrival, Bébert has disappeared. The Martin family sets out to find him.

Huckleberry Finn, a mischievous boy, escapes his alcoholic father and joins forces with a runaway slave named Jim. Together, they navigate the treacherous waters of the Mississippi River, encountering various challenges and learning about friendship and freedom.