Two elite snipers, an American named Levi Kane and a Lithuanian named Darsa working for Russia, are given a mysterious mission by their countries: guarding both sides of a deep ravine, unaware of what lies beneath. Levi is stationed in the western tower, guarding the western side, while Darsa is in charge of the eastern tower, overlooking the ravine from the eastern side. Levi is a private contractor unqualified to be a Marine, while Darsa operates in the semi-official world of covert military operations. All they know is that they are tasked with guarding opposite sides of this top-secret location for a year, as part of an annual rotation, and shooting at anything that emerges from the ravine. The sniper replacing him tells Levi that the ravine could be a gateway to hell and is inhabited by "hollow men." He says that in the 1940s, three battalions of 2,400 men were sent in, but none ever returned. The departing sniper is then killed on his way out by the man in a helicopter responsible for extracting him. The snipers are forbidden from communicating with each other. However, a romantic relationship develops while strange creatures emerge from the trench.
The two manage to find an old Jeep and a tow cable and use it to climb out of the gorge, with Levi injured in his leg. Levi discovers that the gorge is a research site for a corporation called Darklake, which wants to use the Hollow Men as genetically enhanced soldiers and is prepared to eliminate anyone who discovers this secret. Darklake discovers that the two gorge guards have communicated and sends a helicopter with armed men to eliminate them. When Darklake's team arrives in the helicopter and does not find Levi in the tower, they activate armed drones to kill Levi and Darsa. The duo manages to escape, destroying the pursuing drones and then the satellite camouflage mechanism concealing the gorge. These actions activate the "Stray Dog" protocol, a nuclear weapon originally intended to destroy the gorge should it be threatened. The nuclear blast kills everything within the blast radius, including Darklake's helicopter, along with everyone on board. Levi and Darsa manage to escape.
