Paul and Edith Guetz are so besotted with their son that they make him the fateful promise that he can live with them forever. Twenty-eight years later, with Tanguy still under their roof and showing no signs of relocating, they begin to regret their promise. Although she is proud of her son, who is both excessively smart and handsome, Edith is driven to distraction. She makes plans to bundle Tanguy off to Asia. When this doesn't pan out, Edith convinces Paul that they must resort to more serious measures.