Aldo Sax is an FBI agent using "anomaly theory", a method that correlates seemingly unrelated data into a cohesive whole, to investigate three seemingly unrelated ritual murders around the United States. His investigation leads him to a nightclub in Red Hook, Brooklyn, where he hears of a psychoactive drug called Aklo, peddled by a mysterious veiled man named Johnny Carcosa. Sax sets up a meet with Carcosa at the dealer's apartment building, where he is given a hallucinogenic white powder as a prelude to the Aklo. Carcosa speaks an unknown language to Sax, who experiences visions of spectral planes and hideous primordial creatures, while understanding the truth that Aklo is not a drug, but the language Carcosa spoke to him. The visions, given to him by Aklo, drive Sax to murder his neighbor using the same modus operandi as the killers he was investigating.