Despite the upcoming wedding and the appointment of the groom as the Grand Master, Riley Blackthorn tries to protect Atlanta from the hellspawn. Knowing the consequences, she leaves a high-level demon at large, claiming to be free from Lucifer's power. Denver Beck has important events: taking the vows of a Grand Master and husband. He has dedicated his life to fighting darkness, but is worried about his upcoming marriage. His fears about the future come true when a sulfur cloud hits the city, killing its inhabitants. The work of Hell or someone else? It's Beck's job to figure this out. With most of the cities destroyed, Rome calls Riley to account. If she and Beck want a future together, they need to take a stand. But will they survive a new threat, a killer that even the angels fear?