In the heart of the Jura mountains, a strange call is heard at the end of winter. The stately silhouette of a boreal lynx stalks among the beech and fir trees. He is calling to his mate. By following the life of this couple and their kittens, we discover a world that is close to us and yet unknown... An authentic story in which chamois, eagles, foxes and ermines are witnesses to the secret life of this feline – that largest in Europe – which remains under threat... This film discovers the essential role that this shy predator plays in our forests, the balance that it has restored in a fragile environment but also the difficulties it faces in a landscape largely occupied by humans.