Otto Friedrich Dennert is a celebrated veteran of the Essen police force. While investigating a series of killings of women he reaches retirement age. The case is taken over by a new team, including Dennert's son Harry. Convinced that they have arrested the wrong person, Dennert begins investigating by himself with assistance from the criminal underworld.

L'Alpagueur is a free-lance spy from the French secret agency. He's put on the investigation about L'epervier, a serial-killer who employs young boys to help him robbing banks before killing them.