Jönssonligan & den svarta diamanten

Also known as Jönssonligan och den svarta diamanten, Jönsson-Banden og den sorte diamant, The Jönsson Gang and the Black Diamond

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.