The BAU travels to Santa Monica when immolated bodies start showing up on the pier. Identifying the victims proves difficult, but the team soon learns that their UnSub is targeting members of the local homeless community. As they uncover move evidence, they soon learn that they are chasing a killer who is attempting to 'cleanse' what he believes is a diseased class of people. While working the case, Agent Rossi reconnects with his sergeant from the Vietnam War who has been living in a Santa Monica homeless shelter.