Alex Sawyer is a normal teenager until he is wrongly convicted of murder and sentenced to Furnace Penitentiary, a maximum-security prison buried deep beneath the earth. Inside, creatures in gas masks stalk the night, towering guards drag screaming inmates into the dark, and an all-powerful warden pursues experiments that transform boys into monsters. With no hope of a fair trial, escape is Alex's only option.

Alex is a street-smart, morally grounded teenager who refuses to accept his fate. Despite the brutality of Furnace, he holds onto his conscience and his friendships, especially with Donovan and Zee, even as the warden's experiments threaten to extinguish everything that makes him who he is.

Across five books, Alex progresses from desperate prisoner plotting a daring breakout to reluctant monster fighting the darkness injected into his very bloodstream. The series escalates from claustrophobic horror inside prison walls to a full-scale battle for the surface world, exploring themes of wrongful punishment, the cost of survival, and what it means to remain human when humanity is stripped away.