Sickan, the leader of the criminal Jönsson gang is incarcerated in a mental institution, attended by Dr M.A. Busé, who admire a handbook in crime that Sickan has been writing. Blackmailed by the nefarious banker Wall-Enberg, Dr Busé and Sickan's partners Vanheden and Dynamite-Harry execute Sickan's plan of stealing the valuable Black Diamond of the Romanovs from the National Museum.
Sweden 1958. In a small provincial town there is a band who plays dance music twice every week. All decisions are made by Sven Klang, the undisputed leader of the band. A new member joins them, saxophone player Lasse. He starts to criticize Sven's decisions, questions the way they divide the money and he also wants them to be more of a jazz band.
An officers kadett is dismissed because of his strange behavior. At work he is considered deranged. At home he is dominated by his mother and fiancee. He manages to get a temporary job as a biology teacher, leave home and rent a room. He begins to flirt with a student.