A famous industrialist is murdered at a restaurant in Malmoe. Police inspector Martin Beck in Stockholm gets the case. The suspects lead to people involved in illegal arms deals. But who was the biggest criminal, the murderer or the industrialist?
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...
When the people of a small corrupt town find out a secret inspector will be arriving shortly they panic, something which a lazy civil servant takes full advantage of and lets them believe that he is that inspector.
