The riveting story of the hunt for a Berlin serial killer at the height of Nazi rule, uncovering the deep connections between German criminal science and policing and the horrors of the Holocaust.

December 1940, Berlin. Under the cover of citywide blackouts, the city’s commuter rail system, the S-Bahn, became a crime scene. Women were repeatedly attacked on its train cars and thrown onto the tracks below. The police launched a monthslong manhunt to apprehend the murderer.

But even as investigators struggled to stop the “S-Bahn killer,” they were preparing to carry out mass murder on an unprecedented scale.

In When Murder Rode the Train, historian Benjamin Carter Hett reveals the true crime story of how Nazi police worked to stop a killer while becoming killers themselves. To find their target, German police chief Arthur Nebe and his superior Reinhard Heydrich deployed the latest forensic advances in fingerprinting and blood analysis. They also pursued “preventive policing,” scrutinizing ethnic groups suspected of criminality. Soon, they would deploy these same tools to mark people for death in the genocide to come. This real-life detective story reveals that Nazi crime fighters and Holocaust perpetrators were one and the same, showing the criminological ideas at the heart of some of humanity’s worst crimes and asking just how far contemporary policing has really advanced beyond its morally dubious origins.