After his voyage across the galaxy, Nate Silva arrives home to find Hamilton in the grip of a monstrous triumvirate. The Resurrection Church of the Ancient Gods has returned, with the human form of the shape-changing nightmare from the Medusa Deep as its leader. And closely guarded in a downtown tower a mind-devouring entity called Oracle lurks. The city is infested with invasive species that have slithered into our world during the Church's occult ceremonies – many-legged dritches, bat-like thrals and the eerie, flying night-gaunts. Caught in the middle of this are Nate's friends Megan and Mehri, who are leading the resistance with the Furies, along with a mysterious double agent, the enigmatic Dr. Eldritch and his Cosmic Wonder Circus. For the safety of everyone he loves, Nate and his friend H.P. Lovecraft hijack the antique airship Sorcerer for one last voyage, to free Earth from the Great Old Ones once and for all.