The investigators were gathered by Janet Winston-Rogers, heiress to the Winston Pharmaceuticals business to look into events in 1924 when her father, Walter Winston, was an armchair occultist battling what he considered to be some supernatural threat. Following a series of increasingly desperate letters from a man named Douglas Henslowe, the investigators go to Savannah, GA to interview the man himself.
At Joy Grove Asylum, the investigators meet Henslowe after a few disturbing incidents. Douglas Henslowe reveals that he, Walter Winston, the "fixer" Vince Stack, the reporter Katherine Clark and F. C. Kullman, an expert on the occult, traveled across the country combating a perverse cult which venerated something Winston called "The Thing With A Thousand Mouths", often with orgiastic rites fueled (chemically and financially) by drugs.
A confrontation ensued at a barn outside of Los Angeles in 1924, leaving Vince Stack, Katherine Clark, F. C. Kullman, the cult's leader "Echavarria", and many other rank and file cultists dead either from fire, bullets or the grotesque deity the cult managed to conjure. Henslowe and Winston both fled, as well as the ritual's apparent subject- a man named Edgar Job.
Henslowe made his way back East to Savannah and began a long period both in and out of Joy Grove. He confides in the investigators that he recorded all that he remembered from the '20s in a journal, buried at the family estate.
An interview with Edgar Job confirmed the events as Henslowe remembered- including the horrific summoning. Job also went into detail about the cult's extensive drug use, "crazy sex parties" and how Echavarria would consult "old books" for things to say while they all fornicated. After drawing him out a bit, despite Dr. Keaton's misgivings, Job talked about how he was inducted into the cult by a George Avery or maybe Ayers while he was a student at UCLA. Echavarria promised them power when "Gol-Goroth" or the "Fisher From Outside" came, including Job specifically- even going so far as to place a spell of some kind on him on the night of the confrontation. Job survived by stabbing Vince Stack to death and fleeing the scene. Echavarria apparently met his end that night and Job believes he had a mansion in the hills somewhere around LA- possibly in Pasadena or Highland Park.
Leaving the asylum, the investigators visit the sinking Henslowe estate on Moss Island Peninsula. Despite the groundskeeper's unfriendliness, the darknes and the rain, they solve the riddle left for Walter Winston and find Henslowe's journal buried in the family plot along with a safe deposit box key for the First Bank of Long Beach (where the '24 investigators' materials should still be found) and a mysterious stone carved with warding glyphs.
Thugs attempt to run the investigators off the road on the way back to town and then attempt to give them a beating at the airfield later the next day- a mix of white and asian men, the leader of which spoke some strange language full of vowels.