30-year-old factory worker Simon lives a solitary existence on a decrepit farm in the remote French countryside. Devoting his time to caring for his sister Estelle, who was left severely disabled when a childhood game went horribly wrong, Simon is plagued by guilt and depression. But he sees a way out, looking to otherworldly forces as a means of liberating both himself and his sister from the corporeal prisons in which they are confined.
At the end of the 19th century, Joseph Ferdinand Cheval, is a simple postman who travels every day along the Drôme, from village to village. Alone, he is upset when he meets the woman of his life, Philomena. From their union Alice was born. For this child he loves more than anything, Cheval then throws himself into a crazy gamble: to build her with his own hands, an incredible palace. Never spared by the ordeals of life, this ordinary man will not give up and will devote 33 years to build an extraordinary work: "The Ideal Palace".