Like every year, Inès takes the train to Mont-de-Marsan to spend a week's holiday with her grandmother. But this time around, things do not happen as usual. First, Granny is late to the appointment outside the station. And when she finally arrives, she looks strange, seems to have difficulty in finding her way back home and mostly seems to be hiding something for her granddaughter...

David, a professor of dermatology, has been treating 13-year-old Romain since he was a baby. Afflicted with a rare skin condition, Romain must avoid sunlight and is condemned to live in the shade. David and Romain have become the closest of friends and nothing can separate them. But then David learns that he is about to be transferred to another clinic in another town. How will he be able to break the news to Romain? And how will Romain cope with this new crisis in his life?