For years, the top secret British government organization SOE Q, informally know as the Laundry, has guarded mankind from paranormal threats from our own universe and beyond.

The existence of the sentient subaquatic species, codename Poseidon Alpha, has been kept a carefully guarded secret from the public and from all but a select few of the world's governments. A centuries-old noninterference treaty with the sea-dwellers is about to expire, however, and a rival species, codename Varuna Nine, has suddenly made its presence known as well, demanding a role in the negotiations.

Top agents and representatives of SOE Q have been summoned to the hidden seaside town of Dunwich to negotiate new treaties. Something else is going on, too, though -- base computer stations have been shutting down mysteriously, and there have been rumors of demons being sighted in abandoned corners of the base...