Regal is a young Incubus who has recently earned the title of Prince of Lust from Jackal, the King of Hell. Although he is different from all of the other Incubi, he has earned the title for his many successes of capturing lustful souls. That, and he has the perk of being Jackal's son.

Keir is one of Gloria's archangels in training, who specializes in the Virtue of Kindness under the guidance of Michaelangelo. Despite being very powerful for his young age, he still has a lot to learn about earth and its inhabitants before he can move up in the ranks of the Angelic Hierarchy.

These two powerful forces collide when a battle over a human's life goes awry. Keir finds himself head over heels in love with the demon, and Regal is given the rare opportunity to seize the angel as a personal servant. Regal jumps at the chance to become the first demon in history to covet an angel, but Keir is much smarter than he anticipates, and the two end up tethering their souls together in an unbreakable bond.

Keir is more than happy to have the bond between them, but Regal wants out of the deal. The only way to do that is to make the angel fall from grace and become a demon. But can Regal succeed in his plans before Keir makes him ascend into heaven and become one of Gloria's children?