Criminal police commissioner Sabina Nemetz is extremely surprised to find, in the main BKA building in Wiesbaden, a woman in monastic clothing who claims she wants to confess to a crime—specifically, and exclusively, to Sabina’s colleague, Marten S. Schneider. After a heated argument with the new BKA leadership, he quits, so Sabina has to replace him. The words she hears take her breath away: an apparently harmless old nun says that over the next seven days she will commit seven murders—keeping silent about the motive and method. The elderly nun is detained, and at the BKA chaos begins—especially after Sabina, despite all efforts, fails to prevent the first killing. Very soon it becomes clear that behind it all lies an exquisitely intricate plan that intrigues both Sabina and Schneider. He returns to the BKA and, together with Sabina, gets drawn into the game of the nun—unaware of what dark abysses this unpredictable rival will involve him in this time…