Country Dr. Robert Koch is desperate: a tuberculosis epidemic is decimating the children in his district and no one is able to do anything about it. Every fourth child is already sick and the parents must helplessly watch as their young ones die. Now Koch is undertaking to find the cause of the tuberculosis --- something he has already been working on for years --- which has been causing this plague of illness. His work is made more difficult by envy; for example, that of his teacher, who was wounded defending his honor. But his greatest obstacle is the famous Berliner scientist and Reichstag deputy, Privy Councilor Rudolf Virchow: He is extraordinarily skeptical of Koch's theory, that the cause for tuberculosis is a bacteria.

Six German boys visit the zoologist writer Bengt Berg in Sweden where they are shown film footage of water animals, migratory birds and elephants in the Nile area, narrated by the host's naturalistic adventure stories.