When his mother dies, Brian Carter is surprised to learn that he has inherited The Sanctuary, home to her controversial experimental addiction treatment center.

Despite their misgivings, they follow a secret passageway underground and come across strange and unsettling discoveries that trigger Brian's disturbing memories of his mother's research.

Ultimately, they are confronted by her terrible secret: Brian's mother built a revolutionary machine that cured people of their addictions but, as a side effect, those addictions materialized in the form of mutant children hungry for human flesh.

Sharing the dark bowels of the building with swarms of firefly-like creatures that they use to lure their victims into death traps, the mutant children begin a wild hunt, with the new visitors as their prey.

Fighting to stay alive against the inconceivable, Brian and his friends soon realize that some things are better left hidden.