Bestselling author Anja Friedrich is found dead—cause of death: poison! The first suspects are revealed by her extraordinary private life, as Anja Friedrich lived with not one, but two men. The author had written about this threesome relationship in a book. In her bestseller "Monogamy – a thing of the past?", she shared her insights into the joys of love as a threesome. For Mick, it's clear: it was one of her partners. But there are other suspects...

The unassuming librarian Karin Hentschel has been murdered. Mick and Andreas investigate and uncover her surprising secret: she was a sex addict! She had been trying to get her addiction under control in a support group. Mick has to learn a lot about "nymphomania" and "Don Juanism" and quickly realizes that everyone in the support group has something to hide. Mick's investigation focuses in particular on the attractive leader of the group.