1978. The dreams of Didier Mathure, a brilliant space engineer, literally go up in smoke when his rocket explodes on take-off. Just when he thinks he has hit rock-bottom, he is transferred to head GEPAN, a unit specializing in UFOs, run by a team whose members do seem to be living on another planet. He is tasked with coming up with scientific explanations for the UFO sightings that are currently dominating the headlines. This is a nightmare job for an out-and-out rationalist like him, and he is determined to find a way out as soon as he can. But an extraordinary event unsettles his convictions and opens the doors to a world where anything is possible.