Prentiss doesn't look happy after receiving a bouquet of flowers from Andrew. Then she ducks his call. She's lost in thought during a budget meeting. Three men were killed and decapitated in Denver, and the unsub took the heads. After the third killing, he recorded a video message on the victim's phone: "Everything you know is wrong, and this is proof." The unsub is taking advice from a demon. Andrew moved to Denver two months ago to be closer to his daughter. Prentiss shuts down any discussion of that topic. She tells Andrew they'll talk when the case is over. The unsub is targeting father figures. The unsub takes another victim. He is imprinting a mathematical formula onto the victims. He is trying to cross over to a parallel universe. He is affected by the shared false memory phenomenon known as the Mandela Effect. The unsub is a self-loathing father. Andrew confronts Emily about her recent behavior. She admits that a long-distance relationship is harder than she expected. He wants to know where they stand before she goes back to D.C. Garcia discovers that the third victim's caseworker, Brenda Hacker, has an unusually high placement rate of children for single dads. The unsub attacks another man then takes his two teen children hostage. The unsub is George Kyle Peters, whose son Ethan was decapitated in a car crash seven years ago. Kyle had been in a coma then has been in and out of mental institutions since waking up. Brenda worked with Kyle. She has also been extorting money from single fathers to secure custody. Brenda points out a remote area where Kyle took his son on weekends. The BAU finds the cave where Kyle was holding the teens. Prentiss stays behind and joins Andrew and his daughter for dinner.