The cryptic document, apparently written by Dr. Armitage, references a sanitarium, recently built. The patients and staff have secrets worth investigating. There is also a yacht club in nearby Kingsport, which might have information about this strange case. The investigators begin their work, but even a cursory amount of research is not without its risks.
The investigators have solved the mystery of the book only to find a more vexing document-based enigma. Dr. Henry Armitage has produced a letter, seemingly written by him, that he has no memory of writing. The letter warns of an apocalyptic future for humanity, a disaster that might still be averted. The investigators must determine if it is a hoax, the result of a latent madness in Dr. Armitage, or something supernatural. The references it makes are vague yet still connected to Arkham country. The hunt for the truth is on!