Lena Odenthal and Mario Kopper take up the investigation when an animal keeper is found murdered at a horse farm. The man was stabbed at night on the edge of the paddock. Case analyst Johanna Stern is also quickly involved, as the murder may be related to a current series of horse molesters. Did the perpetrator want to attack a horse at night and was surprised by the groom? Was the murdered the victim of unfortunate circumstances or was the actual crime aimed at himself? Lena and Johanna are increasingly investigating in the direction of the alleged horse molester. But they also come across inconsistencies on the horse farm and the mysterious wife of the stud farm owner.
Over time, Lena, Johanna and Kopper manage to narrow down the circle of suspects, but the horse molester seems to be up to mischief. And the evaluation of the course of events and the perpetrator's profile give rise to terrible fears: Is the perpetrator a "living time bomb"? Will he sooner or later try to live out his sadistic fantasies not only on horses, but on a human being?