The six friends who embark on the caving expedition are all experienced adventurers, but tensions quickly begin to rise between them as they descend deeper into the cave system. The collapse that traps them underground also separates the group, leaving them to fend for themselves in the darkness.
As they navigate the treacherous underground tunnels and try to find a way out, they begin to encounter a strange new species of creatures that are adapted to life in the darkness. These creatures are blind but have incredible hearing and a fierce appetite for flesh, which makes the friends easy prey.
As the group is hunted by the creatures, they also turn on each other, with interpersonal conflicts and grudges coming to the surface. The group begins to splinter and alliances are formed and broken in the fight for survival.
As the friends struggle to find a way out of the cave system, they must overcome their own inner demons as well as the external threat from the creatures hunting them. The movie ramps up the tension and horror as the friends are pushed to their limits and forced to make difficult choices in the face of death and despair.