Theo Tan and his fox spirit, Kai, are willing to go to hell and back for their family. Literally. After exposing the corruption at Reapling and trapping the demon king Niu Mo Wang, Theo and Kai learn that Jamie (Theo's beloved brother and Kai's first human master) is trapped in a waiting room in Diyu. If they can reach his soul before it faces judgement they have a (very) slim chance of getting Jamie back! But a trip to Diyu is no easy matter, and Theo and Kai can't do it alone. Fortunately, they have good friends who are happy to help. Still, even with Namita's knowledge and Danny's powerful dragon familiar, the odds are stacked against them. Can Theo and Kai's new bond hold up against lying demons with grudges, impatient Kings of Hell, and the wrath of the Demon King's powerful wife, Princess Iron Fan?