Two fallen angels, Loki and Bartleby, discover a loophole that could get them back into Heaven, despite being eternally banished. If they succeed, it would prove God fallible and erase existence. To prevent this, the angel Metatron recruits Bethany, a disillusioned Catholic woman who works at an abortion clinic, to stop them. She is informed that her lineage is significant and that she is the last Scion, a descendant of Jesus Christ. Along her journey, Bethany is joined by two unlikely prophets, Jay and Silent Bob, as well as Rufus, the 13th apostle who was omitted from the Bible, and Serendipity, a muse who has lost her inspiration.

As they travel to New Jersey where the angels plan to exploit the loophole, Bethany and her companions face a series of challenges. They are pursued by a sinister demon named Azrael and his gang of Stygian triplets. They also encounter various celestial and infernal beings that test their resolve. The group learns more about the nature of faith, the intricacies of divine plans, and the importance of their mission. Each character brings their unique perspective and skills, forming a motley yet dedicated team determined to save humanity from obliteration.