The night of a music festival, a girl is found by the side of the road. She is confused and disoriented. A little further into the forest, a group of teenagers is celebrating the start of summer to techno music, but the atmosphere is not particularly festive… Earlier that day, they had taken part in a "no mobile phones, no connected devices" orienteering course, and two of them are missing. Where are Roxane and Rafaël? Meanwhile, police captain Antony Marin rushes to his injured daughter’s bedside…