Paget Brewster joins the cast as Emily Prentiss, a new agent assigned to the Behavioral Analysis Unit. To her surprise, she has to immediately fight suspicions of nepotism (her parents are high-powered diplomats) as she was placed in the BAU without Hotch or Gideon being notifed.

Meanwhile, the team is dispatched to Saint Louis to track down two serial killers operating concurrently but independently. The killers' M.O. and victims are vastly different from one another, yet the team discovers a surprising connection.