Champion is a melancholic little boy, adopted by his grandmother Mrs. Souza. Noticing his passion for cycling, she makes her grandson follow a relentless training. The years go by. Champion has become an ace of the small queen, so much so that he finds himself engaged as a rider in the Tour de France. But during the race, he is kidnapped by two mysterious men in black. Madame Souza and her faithful dog Bruno set out to find him. Their quest takes them across the ocean to a megalopolis called Belleville. There they meet the Triplettes of Belleville, eccentric music-hall stars of the 1930s who decide to take Madame Souza and Bruno under their wing.