Although he's been retired for ten years from the BAU, David Rossi offers his services back to the unit in Gideon's vacant position. Strauss is suspicious of both Rossi and his motive. Meanwhile, Michelle Colucci of Carrollton, Texas finds a missing persons poster of herself pinned on her front door. The police initially treat this poster as a Halloween prank. However, upon further investigation by the police, Michelle goes missing. The inside of her house is plastered with these posters with a false face mask with the word "ONE" scrawled on it. Three days later, Michelle is found dead in a creek. When the BAU arrive on the scene, a second possible victim is identified in nearby Dallas. Enid White is missing with similar missing persons posters plastered outside in the neighborhood around her apartment. The BAU have to work quickly to develop a theory and profile of the unsub, and to find any connection between Michelle and Enid. In working through this case, Rossi takes matters into his own hands against the wishes of Hotch, the boss. Rossi also clandestinely looks through an old case file.