As Pascal plays with his new found toy, he realizes it has a mind and will of its own. It begins to follow him wherever he goes, and not rise, at times floating outside his bedroom window, as his mother will not allow it in their apartment. The balloon follows Pascal through the streets of Paris, and they draw inquisitive looks from adults and the envy of other children as they wander the streets. At one point it enters his classroom, causing an uproar from his classmates. The noise alerts the principal, who becomes angry with him and locks him up in his office until school is over. At another, he and the balloon encounters a little girl with a blue one that also seems to have a mind of its own too, as evidenced by its act of following his. In their wanderings around the neighborhood, Pascal and the balloon encounter a gang of bullies, who are envious of the latter, and they soon destroy his new friend through the use of slingshots.