“The Call of Cthulhu” opens with a note that the following text was found among the belongings of the late Francis Wayland Thurston. Accompanying this detail is a quote from Algernon Blackwood, a famous writer of ghost stories, about the existence of unimaginable creatures. The actual narrative begins with Thurston’s assessment that the mind’s inability to fully understand the universe is a blessing. With this ominous message, he proceeds to tell the tale of how he uncovered forbidden knowledge which continually haunts him. Thurston explains that he first learned of “the thing” in the winter of 1926-27 while combing through the belongings of his deceased grand-uncle, Professor George Gammell Angell. A specialist in ancient languages, Professor Angell had many research files, but one particular box among his belongings catches Thurston’s eye. While he initially struggles to open it, he eventually succeeds and finds a strange-looking bas-relief inside. The disturbing imagery and undecipherable inscription on the sculpture puzzle Thurston, so he looks to the accompanying manuscript, labeled “CTHULHU CULT,” for answers. 

In the first half of the document, Professor Angell had recorded the tale of a young man named Henry Anthony Wilcox who came to him in March of 1925 with questions about the writing on the bas-relief that Thurston found among his uncle’s possessions. Wilcox reveals that he unknowingly created the sculpture in his sleep as he dreamed of a strange, otherworldly city. This prompts Professor Angell to ask him a series of questions, many of which relate to knowledge of a strange cult. Once he determines that Wilcox is unaware of any mysterious societies, Professor Angell instructs him to continue reporting any unusual dreams. Wilcox obliges, but when he fails to show up to a scheduled meeting on March 23rd, Professor Angell tracks him down to find him stricken with delirium and fever. Strangely, Wilcox’s illness suddenly disappears on April 2nd. Wilcox’s story ends there, but Thurston finds other brief interviews and news articles indicating that artists from across the world experienced similarly bizarre dreams and events during that same timeframe.

The second section of the narrative tells the tale of Professor Angell’s 1908 meeting with Inspector Legrasse, a New Orleans Inspector of Police who came to possess a sculpture similar to Wilcox’s. Inspector Legrasse brings his artifact to a meeting of the American Archeological Society in the hopes of translating its inscription. Only one man in attendance, Professor William Channing Webb, has any vague knowledge of the sculpture as he had encountered one among a violent, devil-worshipping cult in Greenland. This detail intrigues Inspector Legrasse and leads him to tell his own story about how he came to be in possession of such a disturbing item. After receiving complaints from locals about voodoo and people disappearing into the night, the police set out to into the swamplands to discover the cause. They found a group of animalistic, naked men screeching and chanting around a ring of fire with a large monolith at its center. The bodies of those who went missing also hung from scaffolding around the fire. 

As the police interrogated the participants, they learned of the Great Old Ones and their leader, Cthulhu. Most of the worshippers refused to give any other details, but one, old Castro, offered more insight into the legends surrounding Cthulhu. The Great Old Ones will lie sleeping in the city of R’lyeh, communicating with humans through their dreams, until the stars align to resurrect them. In the meantime, the Cthulhu cult keeps their memories alive. Thurston understands why Professor Angell would have been particularly intrigued by Wilcox’s sculpture after hearing Inspector Legrasse’s tale, and he chooses to investigate further by visiting Wilcox at his home. Wilcox tells Thurston of his dreams, convincing him that he has no knowledge of the cult.

Section III opens with a news article from the Sydney Bulletin, dated April 18, 1925, that Thurston finds when visiting a friend in New Jersey. The article describes the mysterious rescue of a Norwegian sailor, Gustaf Johansen, after his ship, the Emma, endured a treacherous storm and brutal attack. After learning that Johansen was in possession of a stone idol much like Wilcox’s bas-relief and Inspector Legrasse’s statue, Thurston decides to investigate further and travels to Australia to search for answers. This quest then leads him to Oslo to visit Johansen himself, but when he arrives, his wife reveals that he died after returning from sea. All Johansen left behind was a manuscript written in English, and Thurston convinces her to give it to him. The document tells the story of his journey at sea in greater detail than the Sydney Bulletin article, revealing the horrors of the storm, the Emma’s run-in with the Alert, the ship that attacked them, and the otherworldly island they come upon. The island, marked by a giant monolith rising out of the sea, is none other than R’lyeh, and the crew manages to awaken Cthulhu. Cthulhu kills almost everyone, but Johansen uses the ship to strike it, sending it back under the sea. Now fully believing in the existence of Cthulhu and the depravity of the universe, Thurston prays that no one else will learn of these dark truths.