Ellie Sloan wakes up in an old, decrepit building, unaware of who she is or how she came to be there. As she seeks a way out, is relentlessly pursued by a demonic creature, hell bent on destroying her. Reliving her life one memory at a time, she comes to understand how she came to be in her labyrinth, from her childhood trauma all the way to her present confinement in the old asylum. Along the way, she experiences a phenomenon she comes to call "the shimmering" which enables her to befriend a woman named Helen from another time. In a quest for survival and guided by Helen, she engages in a battle of wits with the creature as she pieces together the story of her life and attempting to stay ahead of her minotaur long enough to find a way out alive.