John Camden doesn't realize he's dying, yet the physical signs are becoming more clear, and he's having recurring visions where he is trapped in a tight space.

Everything changes when his best friend Robbie convinces him to go on a poorly planned caving trip as a form of immersion therapy.

Soon the lines of reality blur as John finds himself lost and alone, deep underground where all is not as it seems, and the person he trusted most may have sinister intentions.