Beneath heaven is hell.

Beneath hell is Furnace.

Furnace Penitentiary. The world's most secure prison for young offenders, buried a mile beneath the earth's surface. One way in, no way out. Convicted of a murder he didn't commit, sentenced to life without parole, 'new fish' Alex Sawyer knows he has two choices: escape or die.

Only in Furnace, death is the least of his worries. Soon Alex discovers that the prison is a place of pure evil, where creatures in gas masks stalk the corridors at night and deformed beasts can be heard howling from the blood-drenched tunnels below. Behind everything is the terrifying warden, whose powers stretch far beyond the walls of the prison.

Together with a bunch of inmates, Alex plans the prison break to end all prison breaks...