The team heads to Los Angeles, California where three people have been murdered in two separate incidents over three days, each victim shot thirteen times while sitting in a car or next to a car located in the same crime ridden neighborhood. The ballistics show the same .45 caliber gun was used in both instances. The first victim, Gary Fisher, was known to have frequented prostitutes and was found in area where he was probably meeting with one. Nate Cochran and Tasha Brooks, the second and third victims in the same car, were a john and a hooker. When a fourth and fifth victim are discovered together, they an elderly woman, Clara Miller, and who seems to be a mugger, Lamar Taylor, the team believes the unsub is a vigilante - a moral enforcer - who is looking to clean up the streets of what he sees as immoral behavior. Because of the overkill, they know the reasons for the murders are personal. Information they learn about Clara and Lamar, and the discovery of subsequent victims leads to the team believing the unsub is devolving into believing everyone is a criminal. As such, they have to put together the pieces quickly to find him before more innocent people are indiscriminately killed.

When Kate's niece and her best friend Markayla are kidnapped, the BAU suspects an online predator engaged in sex trafficking who poses as a teenage boy.