In Milwaukee, a series of women have been found murdered with their hearts crudely removed. The BAU is assigned to the case, but they are short three members: Gideon, who is missing, Hotch, who is on suspension and Prentiss, who resigns her commission to join the Foreign Service. Supervisor Strauss steps in as lead, but she doesn't handle herself well in the field.
Meanwhile, another woman has been kidnapped, and judging by video footage from her last known location, she was lured by a child decoy. The team formulates a profile for the killer, and recognizes that they should be looking for a child who stands out from the crowd. Back in DC, Hotch has a change of heart (after a chat with Garcia) about working the case, and he convinces Prentiss to join him on one last case.
A teacher identifies one boy, David, whose father has been diagnosed with a fatal brain tumor. The boy's mother abandoned them despite the illness, driving the father to kill. The team speeds to the father's home, and they manage to rescue a school nurse who drove David home from school. The father is taken into custody, though he'll die before he stands trial.
After the case ends, Reid locates the cabin where Gideon has been staying. Inside is a note addressed to Spencer. With the note are Gideon's gun and badge. Gideon has left town, heading out on the road to "nowhere in particular," in search of a happy ending.