Inspector Frans J. Palmu, depicted as "a gruff detective of the Helsinki police department", is one of the most popular characters created by Finnish writer Mika Waltari (who is, however, better known outside Finland for his historical novels). The first movie was produced by Suomi-Filmi and the latter three by Fennada. Joel Rinne plays Palmu in all four films and is accompanied by his jack-of-all-trades assistant (later restaurant owner) Väinö Kokki played by Leo Jokela and Toivo Virta the university-educated officer (who eventually outranks Palmu) played by Matti Ranin.