It's 1972. Six-and-a-half-year-old Sébastien Martin is a sensitive, highly imaginative child. Despite the affection he feels for his father, a dreamy inventor, he notices his mother's loneliness and how there is a lack of love in her life. When the Martin family moves house, it won't be long before Sébastien sees in Philippe, his new neighbor, an ideal Prince Charming for his mother.