The body of Sergej Radev Nikolov is found in the middle of Ludwigshafen. A suspected hitman who was in town 15 years earlier and was implicated in the murder of a chemist. Mark Moss, friend of the murdered man and now about to jump into the management board of the chemical plant, presents himself to Lena Odenthal and her colleagues Kopper and Johanna Stern as an inexperienced clean man. But he doesn't convince Lena. shekeeps an eye on him and meets a man who she had already noticed near the scene of the crime. Lu used to be a debt collector and then suddenly disappeared. Lena's instincts tell her that Lu's appearance and the assassin's return must be related. It is not easy for her to accept the suspicion that Lu Wolff seems to be involved in her case.