When Arthur Carsdale, a graduate student in the history department, accidentally triggered the sealing spell of the Old God in a 17th-century manuscript, his consciousness was dragged into Arkham City in the 1920s and possessed by a dying young man of the same name. He soon discovers that the world is far more terrifying than what games and novels depict—the Great Old Ones are not fictional, and they are awakening. What's even more frightening is that there is an unexplainable mark on his wrist. It is a "shackle" left by an old god and a "key" that the old rulers are eager to seize. In order to survive and find his way home, Arthur must learn to use forbidden knowledge, dealing with all kinds of crazy forces on the edge of the collapse of his sanity.
