Despite the enthusiastic anticipation of the city's residents for Halloween, a series of horrifying child abductions make their way to Portland, quickly spoiling the holiday spirit. Nick and Hank join forces with Valentina Espinosa, a mysterious detective from Albuquerque, to help find and capture the elusive suspect. Juliette joins their investigation, acting as the precinct's fill-in Spanish translator. The more Nick digs into the case, the more he realizes the pattern of the kidnapping matches those in the famed Hispanic horror story "La Llorona," a story with its roots intertwined with his own family's history. Meanwhile, Monroe celebrates the holiday in fine style as he teaches the neighborhood bullies a lesson.

Hank starts reflecting on an arrest he made earlier in his career regarding a man who committed murder claiming "self-defense against monsters." With the man's death sentence rapidly approaching and the knowledge he's recently gathered from Nick, Hank begins to wonder if there was more truth to the man's seemingly absurd story then he once thought. Back at the spice shop, Monroe finds himself involved in a situation he never saw coming.