When Prince Vain got his shirt fixed, he proclaims that he had slain two lizards in front of the tailor's house - "two in one strike". When the tailor swats seven flies at once, he sows himself a banner saying "seven in one strike", and together with his bird he starts a journey into the world to pronounce his deed.

Engineer Franz Bach seems to have gone astray once again. Working overtime, nagging at his wife and his parents sleeping apart lead the children to come to this conclusion. It can't go on like this. His youngest son Täve does his best to keep his father away from the very young intern Irene. Täve's 19-year-old brother, on the other hand, tries to steal his father's mistress. His wife Margarete also wants to bring a breath of fresh air into the marriage.

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.