The cave Karyn is about to sneak into has a gory history. Often spelunkers and cavers will emerge from the caverns with a lust for blood, supposedly driven mad by beautiful music heard in its depths. But when the woman Karyn loves, Pree, disappears in the caverns with a team of cavers, Karyn knows she’s the only one who can save her. Karyn possesses a rare form of synesthesia that allows her to feel sound; this makes her the only caver who can survive an expedition while she wears headphones to drown out the music. As she descends, she’s horrified to encounter the dead body of an expedition member, and another driven to madness and bloodlust. He attacks Karyn and kills himself by eating rocks until he chokes. At last, Karyn reaches the source of the music. It’s a bacteria that imprisons cavers, slowly entombs them in stone, and uses their vocal cords to lure more victims into the depths. Pree is the one singing; half her body is entombed in stone and a spike runs through her chest. Karyn gently pulls her from her forming sarcophagus, and Pree dies in her arms. Karyn struggles back to the surface to warn everyone away from the cave. She emerges and discovers much of the town and several backup expeditions of cavers. Her mouth opens and she begins to sing; the bacteria have made her a host. The people tear each other apart.