Building on Book 3 of the Dogmatics’s consideration of creation and grace and anticipating Book 5’s treatment of salvation, Book 4 of Scheeben’s Handbook of Catholic Dogmatics presents his theory of sin and its concrete realizations among the angelic order and humankind. Notable is his stress on the character of original sin as an offense against the supernatural order, that is, against our adoptive sonship—and so as the biblical mysterium iniquitatis. Also noteworthy is the nuanced way he handles the relation between sin as a privation of grace and the wounding of human nature, original sin’s hereditary character, and the mysterious nature of angelic sin.