I would say it's a pleasure to meet thee, Prosperity Oceanus Redding, but truly, I only anticipate the delights of destroying thy happiness. Prosper is the only unexceptional Redding in his old and storied family history—that is, until he discovers the demon living inside him. Turns out Prosper's great-great-great-great-great-something grandfather made—and then broke—a contract with a malefactor, a demon who exchanges fortune for eternal servitude. And, weirdly enough, four-thousand-year-old Alastor isn't exactly the forgiving type. The fiend has reawakened with one purpose—to destroy the family whose success he ensured and who then betrayed him. With only days to break the curse and banish Alastor back to the demon realm, Prosper is playing unwilling host to the fiend, who delights in tormenting him with nasty insults and constant attempts trick him into a contract. Yeah, Prosper will take his future without a side of eternal servitude, thanks. Little does Prosper know, the malefactor's control over his body grows stronger with each passing night, and there's a lot Alastor isn't telling his dim-witted (but admittedly strong-willed) human host.

Three hundred years ago, fate bound Prosper Redding and Prince Alastor of the Third Realm together. Now the human boy and fiend heir to the demon kingdom must put aside a centuries-old blood feud to save everything they love. Alastor will guide Prosper through the demon realm—under one huge condition: Prosper must enter into a contract with the malefactor residing in him, promising eternal servitude in the afterlife. With Prosper's sister in the clutches of the evil queen Pyra, Prosper has no choice but to agree. But when they arrive in Alastor's deliciously demonic home, the realm is almost as alien to Alastor as it is to Prosper—the lowest fiends have dethroned the ruling malefactors, while an unfathomable force called the Void is swiftly consuming the realm. The desperate fiends cling to the one person who says she can stop it: Pyra. As Prosper embarks on a perilous rescue mission to the Tower of No Return, he can't help but feel for the demons losing their home—even Alastor, who lives by a set of rules that have vanished in a new world. With the fates of humans and demons at odds, the battle lines are drawn. Long ago, Prosper's ancestor Honor Redding proved that humans and demons could never be friends. But is Prosper like his ancestor? And is Alastor the same demon who was betrayed by the one human he cared for?