Rossi counsels JJ on how to handle Barnes. An invader kills four housemates in St. Louis. Barnes called and offered the BAU services to St. Louis police, rather than the other way around. Barnes is going into the field with them. Reid refuses to go if Barnes is going, and takes a sick day. The knife used to kill the victims came from within the house, so an insider was involved. Prentiss is already packing up, thinking that her leaving will save the BAU. One of the living roommates, Larry Scanlon, is the prime suspect. Rachel, another roommate, tells Lewis and Barnes where to find Larry. But he gets suffocated before they find him. It's staged to look like a drug overdose, complete with a suicide note claiming responsibility for the murders. JJ said it was staged. Prentiss tells Reid that she deleted his incriminating statements while in prison. That's why she feels she needs to leave. Rossi said the roommates were like a family, and the unsub is a family annihilator. Barnes won't let Lewis and Simmons tell Rachel Larry is dead. Rachel identifies Justin Franco as the person who fits the profile. Reid tries to talk Prentiss into staying, to fight for the team, and she agrees. Justin wants to have Corinne, the flight-attendant roommate, for herself. He's trying to transform himself into Ray, on whom Corinne has a crush. Simmons confronts Barnes about her trying to end the BAU. The team hopes to intercept Justin at the airport. Alvez and Lewis confront Justin, who pulls a gun and threatens to kill himself. Barnes brought out Corinne despite JJ's warning. An enraged Justin shoots Corinne, then Alvez shoots him. JJ gets into it with Barnes before takeoff. Barnes gets permission to restructure the BAU.