Heatwave. Max Hammerschmidt, #1

Max Hammerschmidt, a former foreign legionnaire and tough private detective, faces one of the biggest challenges of his life: 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.