Set in a fictional 19th century England, D.Gray-man is the story of Allen Walker, a 15-year-old boy who roams the earth in search of Innocence. Washed away to unknown parts of the world after The Great Flood, Innocence is the mysterious substance used to create weapons that obliterate demons known as akuma.

With Allen Walker once more in their ranks, the Exorcists soldier into the fabled Ark of Noah. In almost no time they encounter opposition in the form of two young Noah possessing startling powers. The Noah, however, seem less interested in the grand plans of the Millennium Earl than in collecting payment on yet another mountain of debt accrued by Allen's master, General Cross Marian. Can the Exorcists find the literal key out of this potentially lethal predicament?