1828 in the Hanseatic port city of Bremen: Senator Droste would like his town to be first in Germany to adopt a railroad line, but temporarily has to serve as president of the Criminal Court. Called upon to investigate a case of rat poison found on food, he believes in routine coincidence. But as a beautiful and mysterious woman asks for his help and protection, Droste and new assistant Cato discover an abundance of fatalities in the Pelzerstrasse neighborhood.