Biographical movie about Julius Robert Mayer (1814-1878), a surgeon and town doctor in Heilbronn, who studied heat for many years and was the first to correctly formulate the basic principles of the theory of mechanical heat and the principle of conservation of energy. Competing Prussian scientists laugh at him, and his life is full of misunderstandings and persecution. The film tells of his fate and his long and futile struggle for recognition of the results of his scientific work.