In a high mountain refuge, Alex Hugo discovers the bodies of Isabelle and Antoine Lindberg. A farewell letter gives details of the circumstances of their death. Isabelle, who was suffering from an incurable disease, wanted to end it. Antoine decided to accompany him on his last trip. The couple asks that their ashes be scattered at the top of the mountain. But Alex is not convinced by these too simple explanations. He wonders if someone would not have made up a double murder in suicide. He begins a delicate investigation...

As the winter is Lusagne, Alex Hugo decides to go on a solitary bivouac. His hike leads him to high altitude, to the snowy peaks. As he climbs a rocky pan, the policeman hears an explosion, which tilts him back. Sounded, he woke up in a snow shower, wounded, his axe piercing his abdomen. He manages to alert his teammates, but they do not know where he is. Alex is finally saved by a mysterious stranger. During this time, in the valley, the research is organized. Only the missing bag is found. Death in the soul, the village resolves to the idea that Alex Hugo died in the mountains...