The great Dr. Pfeiffer plays the little Primaner Pfeiffer. As the successful playwright Dr. Hans Pfeiffer, he is planning a play about school. In order to gather material, he takes the place of his brother, who is a primary school pupil. The seasoned doctor finds pleasure in the craziest of pranks, while his brother tries to fill the role of theater man in the big city. And then love intervenes for both of them.