The Jönsson Gang & the Black Diamond
Instead of being released from prison, Jönssonligan's leader Sickan has been placed in a mental institution. There his psychiatrist discovers that Sickan's notebook filled with scribbles is actually a handbook in crime. Especially carefully written down is a plan to steal Romanoff's black diamond that the Russian state has loaned to the National Museum. Something that suits the psychologist, M. A. Busé, nicely because he is deep in debt. He fools Vanheden and Dynamit-Harry to help him and everything goes as planned. Until Jönssonligan's arch-enemy Wall-Enberg gets mixed up. Aftonbladet's Jens Petersen thought the film was "a success for Peter Haber as Doctor M A Busé" and "A successful comedy for the whole family."