Sophie has gone to Praz in the Alps to investigate about the disappearance of her sister Anne who was taking pictures in these mountains with the help of the guide Sébastien.At the hotel she meets Gustave Berton , the uncle of Sébastien who is mayor of the village.Suddenly there are many cars in the streets of the village: the rescue team comes back with a survivor-the guide Sébastien- who is sent to the hospital.