Paris 1810. Breton doctor René Laennec fights tooth and nail against consumption, all the more desperately as his brother Michaud has just died of it. He is supported in his research work by his senior partner and friend, Doctor Bayle, but this one dies before they are able to diagnose and defeat the "enemy". One day, after observing a children's toy, Laennec discovers the principle of the transmission of sound through wood and applies it to a major medical instrument of his invention, the stethoscope. On the other hand, he wins a first victory over consumption by saving Jacquemine, a childhood friend, who soon becomes his wife. Nevertheless Laennec is the laughing stock of many a fellow-colleague, especially famed Doctor Broussais. But , remaining undeterred, Laennec goes on with his research. He works hard, too hard, until he too gets struck by the "enemy".