Francis Wayland Thurston is an archeologist and careful rationalist living in Boston, Massachusetts. Tasked with settling the estate of his late relative, he applies scientific skepticism to the unusual documents and artifacts left behind. He prefers empirical evidence and initially assumes the bizarre clay tablet he finds is a hoax. His organized mind struggles as he cross-references global news clippings with dream journals.

Professor George Gammel Angell is a respected scholar at Brown University specializing in ancient pictograms and inscriptions. He dedicates the final months of his life to meticulously documenting dream accounts and cross-referencing them with the activities of obscure secret societies. His extensive, carefully dated notes provide the foundation for an inquiry into worldwide supernatural disturbances.

Henry Anthony Wilcox is a young sculpture student at the Rhode Island School of Design who comes from an affluent family. He describes himself as psychically hypersensitive and suffers from periods of feverish delirium. His artistic temperament makes him susceptible to bizarre, otherworldly dreams that feature non-Euclidean cities and monstrous shapes, which he translates into physical art.

Cthulhu is an ancient entity worshipped by hidden groups across the globe. Belonging to a category known as the Old Ones, this massive creature resides in an underwater vault, waiting for a cosmic alignment to awaken. The mere psychic projection of this being induces severe mental distress in sensitive individuals and artists worldwide.

Inspector Legrasse is a police officer who leads a raid on an illegal, disturbing ritual in the swamps of Louisiana. He recovers a small, unidentifiable stone carving of a tentacled monster during the operation. He seeks out academic experts to identify the artifact in hopes of locating the group's headquarters.

Gustaf Johansen is a Norwegian sailor whose ship is blown off course during a severe storm in the Pacific Ocean. He survives a harrowing landing on an uncharted island characterized by unusual, non-Euclidean geometry. He writes an English manuscript documenting an encounter that defies conventional human logic.

Old Castro is a prisoner detained by police during a raid on a secretive gathering. He acts as an informant, translating his group's chants and explaining their theology regarding ancient beings who wait beneath the ocean to bring about global chaos.

Professor Webb is an academic from Princeton University who attends a scholarly conference. He provides the only link to Inspector Legrasse's mysterious statuette, recognizing its similarity to a demonic deity worshipped by an isolated group in Greenland.

Briden is a sailor who lands on an uncharted Pacific island alongside Gustaf Johansen. He encounters architecture and horrors that rapidly shatter his rational mind.