Two highly-trained operatives (Miles Teller and Anya Taylor-Joy) are appointed to posts in guard towers on opposite sides of a vast and highly classified gorge, protecting the world from an undisclosed, mysterious evil that lurks within. They bond from a distance while trying to stay vigilant in defending against an unseen enemy. When the cataclysmic threat to humanity is revealed to them, they must work together in a test of both their physical and mental strength to keep the secret in the gorge before it’s too late.