The school camp of a Catholic Swiss youth group ends tragically when one of the boys is found abused and murdered. At the site where the body was found, Klara Blum and Kai Perlmann meet their Swiss colleague Matteo Lüthi, who is handling the case for the Thurgau canton police. Lüthi, who until recently worked for the Swiss intelligence service, is anything but a team player. Klara, on the other hand, doesn't want to let the direction of the investigation be taken out of her hands so easily. Accordingly, there is a lot of crunching in the cooperation, especially since the nerves are on edge in a case of child abuse. Moritz, the murdered boy's roommate, is convinced that Nachtkrapp, a children's night terror, got his friend.
The inspectors have other suspects: Deacon Franz Hobmann, who looked after the youth group, and Herbert and Andreas Bogener from the school camp. The evidence also speaks against Holger Nussbaum, who has served 15 years in prison for a very similar case and has recently been released. Nussbaum still has an old score to settle with Klara, so when the inspector tries to arrest him, he resorts to desperate means.