Every night in winter, Guillaume travels across the mountains and ski runs on board a snow groomer. Before leaving, the vehicle is hooked onto a steel cable that allows him to descend long slopes that would otherwise be impracticable and prepare the ski runs. Alone in his cabin, Guillaume travels in the company of his thoughts, blown out of proportion by the impenetrable darkness of the mountain nights, dimly illuminated by the electric light of his vehicle’s headlamps. His life is literally hanging on a steel thread.