Puppet theater voice actress Suzanne (Juliette Binoche) lives with her young son Simon (Simon Iteanu) in a tiny Parisian apartment. With her hectic schedule, she has little time to care for the boy and leaves most of her mothering duties to baby sitter Song (Fang Song). As Suzanne becomes embroiled in a court case involving her downstairs tenant, Song and Simon become intrigued by a red balloon that starts following them around the city.