When Brian Karter’s mother dies, he is surprised to learn that he has inherited The Sanctuary, home to her controversial experimental addiction treatment center. Having previously believed that the building burned to the ground years ago, Brian travels there with a group of friends and meets Haley, a mysterious friend of his mother, who acts as their guide through the impressive, monastery-like building. During their tour it becomes clear that something sinister lies beneath the surface.
Despite their misgivings, they follow a secret passageway underground and come across strange and unsettling discoveries that trigger Brianâ™s disturbing memories of his motherâ™s research. Ultimately, they are confronted by her terrible secret: Brianâ™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.