Philippe Perrin, a young engineer passionate about his work, leads the construction of a huge dam in the High Alps. Like all the men who work on the building site, he gives the best part of himself. Unfortunately, his health deteriorates but he refuses to follow the doctor's orders as well as the advice of Micheline, a young nurse who has fallen in love with him. However, driven by the evolution of his illness, Philippe finally makes up his mind to go down to the valley for a treatment. On the very day of his departure though, a young Arab worker gets killed in a rock crusher...