Max Hammerschmidt, a former foreign legionnaire and tough private detective, faces one of the biggest challenges of his the investigation of an old series of murders that the Cologne police could never solve. The Cologne Strangler has killed young women in a cruel way, and the traces have long been cold. When Max is commissioned by a desperate family to resume the investigation, he stumbles upon a world full of secrets, lies and unprocessed trauma. But as he interrogates witnesses and fights his way through a maze of half-truths, his own past catches up with him - the search for his missing daughter. In a brutal heat wave that brings Cologne to a boil, Max must not only hunt down a serial killer, but also defeat his own demons.