Katie reluctantly joins Westport's Halloween zombie run; Anna-Kat and Greg get too enthusiastic about being zombies.
When an anger-driven, unknown subject targets successful businessmen in Detroit, the BAU must investigate.
A guilt-ridden Magnum follows the clues his private investigator friend left behind when he was shot while working a case Thomas passed onto him; TC helps Kumu lead a protest against construction on a Hawaiian sacred site.