A horse wanders from a town to the countryside. Here lives Sten Stensson Steen, a bachelor at law and philosophy. He is writing a social psychological report on the youth problem. In the neighborhood is experimental school Fridhem situated. The neighbors live in fear of school boys pranks and behavior. The principal of Fridhem resigns. The school risks being shut down. Steen signs up as candidates for the vacant principal service. The boys welcome him with clever pranks. He fends off and attempts to transform the boys into well-behaved angels.