In 1984, the renowned author, Salvatore Archimboldi accepts the help of a psychotherapist to write his new book, hoping to transform traumatic memories into literary genius. But the resulting book, The Truth of Carcosa, is more than a book—and, horrified, Archimboldi suppresses his creation and wills all traces of it, his correspondence, and any copies to be totally destroyed.

Long after Archimboldi's death, in a chaotic age of resurgent nationalism and violence, a biographer and his protégée search through Archimboldi's correspondence for clues to the location for the last copy of The Truth of Carcosa. Hot on their heels are a shadowy, all-powerful corporation, and a madman with his own, private reasons for his obsession. As these groups converge, it becomes clear that the last copy of The Truth of Carcosa might be the answer to a bewildering set of questions:

What are the strange entities that arise in the wake of the book?

Who—or what—is the Yellow King?

And what does he want with us?