After a disastrous mission and betrayal from within its own ranks, the London Resistance is shattered beyond repair. Amaranth and the meager remains of the Resistance journey to Vatican City, where they hope to discover the true location of the Demon's Gate. Should they find and destroy it, the demons would be forced back to their own world, and the spell binding Amaranth to a demon would break.

But on their heels comes Raulston, a powerful man hell-bent on crushing an resistance to the demons that are destroying the remnants of humanity. Amaranth and her closest companions—Dham and Cat—will do whatever it takes to ensure humanity's survival. With Amaranth's magical powers, and Dham and Cat's rare ability to kill demons using sacred bells, they might stand a chance against the demon invasion. But as the trio face life, death, and the in-between, their devotion to each other may be what brings their downfall.