Two elite
snipers receive identical missions: guard opposite sides of a remote, top-secret gorge for a year without contact with their counterparts or the outside world. Levi Kane, a former
U.S. Marine Scout/Sniper, is recruited by a mysterious woman named Bartholomew to guard the west tower. Drasa, a Lithuanian covert operative frequently employed by the
Kremlin, guards the east tower. Levi suffers from
PTSD-induced nightmares, while Drasa's terminally ill father Erikas plans to die by suicide on
Valentine's Day. Levi relieves his predecessor J.D., a former British
Royal Marine corporal, who explains that the location is kept hidden by powerful
cloaking antennas and the towers are armed to contain monstrous creatures within the gorge, nicknamed "
The Hollow Men". J.D. warns of "Straydog", an unknown emergency protocol, and that battalions of soldiers sent into the gorge in the late 1940s never returned. Believing he is being
exfiltrated after leaving the gorge, J.D. is instead killed on Bartholomew's orders after being picked up by helicopter. After several uneventful months, Drasa violates the no-communication protocol on her birthday, engaging Levi in conversation via written signs and a sharpshooting competition. A wave of Hollow Men attempt to climb out of the gorge, but Drasa and Levi use their rifles, automated turrets, and
mines to defend their towers and each other. As time goes on, they bond from afar. Six months into their posting, Levi
ziplines across the gorge to have dinner with Drasa. They spend a romantic night together, and he reveals he is writing a poem for her. The next morning, as Levi returns to his tower, his cable snaps when mines are detonated by Hollow Men, forcing him to parachute into the gorge. Arming herself, Drasa parachutes after him. The pair discover that all plant and animal life within the gorge has been
cross-mutated, including the Hollow Men, revealed to be the missing soldiers from decades past. Fighting off the hostile lifeforms, Drasa and Levi find the source of the mutations: a
World War II bioweapons research lab abandoned after an earthquake caused a contaminant leak that produces symptoms within five days. The facility has since been maintained by Darklake, a
private defense corporation extracting hybrid samples in hopes of creating
super soldiers. Drasa and Levi discover Straydog is the original
fail-safe protocol to
sterilize the site with a
nuclear explosion. They find a working
Jeep with a towing winch, using it to climb out of the gorge as they fight off the Hollow Men, and agree to separate for five days to ensure they are not infected with the mutagens. During Levi's monthly radio check-in, Bartholomew admits that she works for Darklake and orders him to kill Drasa. Aware that the two snipers have discovered the truth, Bartholomew dispatches a team to eliminate them. Bartholomew and her men arrive to find the towers abandoned. Drasa and Levi outgun the
armed drones sent after them and destroy the cloaking antennas, exposing the site to
surveillance and triggering Straydog's detonation. Bartholomew and her men are killed in the blast, and the area is destroyed, while Drasa is separated from Levi and completes her five-day self-quarantine. She reaches France to rendezvous with Levi, who does not appear, and discovers that he left her the completed poem in an envelope marked "If I don't make it, open at sunset." Some time later, Drasa has begun a new life as a waitress in a local restaurant. She is surprised by Levi, who says he was delayed by an injury, and they embrace and kiss. ==Cast==