1896 year. New York. The horribly mutilated body of a prostitute boy is found on the unfinished Williamsburg Bridge. The police commissioner entrusts an unofficial investigation of the case to his old friends - a specialist in the study of psychological pathologies, or an alienist, Dr. Laszlo Kreitzler. Dr. Kreitzler's team manages to make a real revolution in criminology — to create a psychological portrait of a serial killer. A dangerous investigation reveals to them a tragic past and the twisted mind of a maniac who will kill again and again until he is tracked down...