It's an unusual friendship, considering that David is 50 and Romain is 13. David, a professor of dermatology passionate about his profession, has been treating Romain and operating on him since he was two years old. Afflicted with a rare genetic disorder, Romain must be protected from daylight. He is a "moon child." It seems that nothing could separate them, until one day David is granted an unexpected transfer. How can he tell Romain that he is leaving? The day of separation draws nearer, bringing new challenges for each of them to face.