Murder in Art Nouveau

Why are the director of the Hagen Osthaus Museum and his deputy murdered? Why is a well-known art forger reactivated? On which wise disappeared valuable paintings from the museum during the Nazi era? And what has the Naples Camorra to do with all this?
Questions upon questions that lead to a real confusion. In any case, the murders are causing excitement in Hagen. The police is initially faced with a mystery. Can this complicated case be solved?