Toward the close of the nineteenth century, Allen Walker formally joins the Exorcists, an organization dedicated to the annihilation of the entities known as Akuma; mechanical weapons created by the Millennium Earl using the tormented souls of the dead. Allen possesses a cursed eye as well as an anti-Akuma weapon, both of which are imbued with the power of "Innocence," a gift bestowed upon him as an apostle of God. Allen and his fellow Exorcists must halt the Millennium Earl's final scheme, which might lead to the annihilation of the Earth and everyone who live on it.