With her wedding fast approaching, as well as her fiance's investiture as grand master, Master Demon Trapper Riley Blackthorne is just trying to keep Atlanta safe from Hellspawn. When she meets a high-level fiend who claims to be free of Lucifer's control, and allows him to remain at large, she knows there will be consequences. Denver Beck is facing two major events: taking his vows as a grand master and then as a husband. He's as nervous about committing his life to the fight against Darkness as he's excited to say, "I do." All his worries about the future are confirmed when a city is buried in brimstone, killing every single inhabitant. Was this Hell's doing, or is some other entity at work? It's Beck's job to find out. After more cities are destroyed, Riley is summoned to Rome to answer for her actions. If they want a future as man and wife, she and Beck will have to take a stand. But will they be strong enough to stop this new threat, a killer that even the angels fear?