The series' main character is Allen Walker, a young Exorcist who trained under Exorcist General Cross Marian and is sent to officially join the Black Order. Early in the series, he is sent on missions with fellow Exorcists. He meets Yu Kanda, a cold and mysterious swordsman looking for a certain person from his past; the friendly Lenalee Lee, who has been an Exorcist her entire life; and Lavi, the cheerful and energetic future Bookman, chronicler of the secret history of the world. They travel the globe, retrieving the pieces of Innocence scattered during the Great Flood and recruiting new Exorcists while fighting the Earl and his Akuma. However, the Black Order soon learns the Earl has help in the form of the Clan of Noah, a group of thirteen super-humans who can destroy Innocence and claim to be the true "Apostles of God". Both groups quickly begin searching for the Great Heart, the most powerful Innocence that can strengthen or destroy all the others, to bring an end to the war.