Harmonic House

The Harmonic House, Massachusetts, was the hideout of a cult who discovered the existence of the Great Race of Yith and came to worship them as gods. It is also the first location Jack visits in the game, and serves at the first level.

The cult :
The Fellowship of Yith was a group dedicated with helping and understanding the Great Race. It was composed entirely of humans, although they had enough resources to build strange machines eerily similar to those used by the Mi-Go race.

At some point during 1915 (or before) their point of interest became Jack Walters, a private detective, whom they started to track down. It is later revealed that this was because of his Yithian ancestry.

The cult was ever loyal to their mission, but that didn't go unnoticed by the local community which was very frightful of them. On the 6th of September this escalated into a conflict between the cult and the local police. Soon Jack Walters was called, since the cult leader Victor Holt would only speak with him.

Awaiting Jack's arrival many of the cult members would commit suicide, while others would die fighting the police. It isn't confirmed if any of the members survived the incident, but it is safe to assume they didn't.

The Underground Labs
Beneath the mansion is an underground complex accessed via a trapdoor in the house library. Amongst others, it contains :
 * A morgue filled with bodies and medical supplies.
 * A room filled with strange machinery designed to keep a human alive with his organs removed from his body.
 * A portal room used by the Yithians to travel through time and space.

Trivia :

 * Even though there is mention of a character called Victor Holt (the leader of the cult), no such character appears in the game.
 * There is a cult aiding the Yithians in the Call of Cthulhu RPG book " Malleus Monstrorum" in exchange for magical and technological knowledge. However, since the book was released several years after the game, it is very unlikely that the Fellowship of Yith have any ties with them.
 * Interestingly, there is some mention in "Fungi from Yuggoth" by H.P. Lovecraft of " a society dedicated to aiding those of the Great Race who travel through space and time to this point in Earth's history." It is however unclear if the Fellowship is part of that cult or if they even knew of it's existence.