When homicide detectives Leo Magozzi and Gino Rolseth are called to a crime scene in a heavily-wooded city park, the setting is all too familiar. And when they discover a playing card on the victim's body, their worst fears are confirmed: there's a serial killer operating in the city for the first time in years. As the violence accelerates in Minneapolis, Magozzi and Rolseth soon realize their killer is planning to complete the deck, and they enlist Grace MacBride and her unconventional partners at Monkeewrench Software to help stop the rampage. As a baffling tangle of evidence accumulates, the cops and Monkeewrench make unlikely connections between a farmer's missing daughter, a serial killer, and a decades-old stabbing that bring them face-to-face with pure evil.