In 2017, the US Air Force dropped its most powerful non-nuclear bomb in a remote Afghan province. Officially it was said they attacked a key insurgent stronghold in the area, but there were rumors of something else happening prior to the bombing. This is the real story. Pilots Kate and Johnson from the Royal Air Force are flying over Afghanistan on their way home when they're suddenly attacked by an insurgent group and their planes get hit. Both pilots eject their seats and when they hit the ground, Kate dreams of her mother and son while holding tightly her locket with a picture of them. Seconds later, Kate is woken up by Johnson, who asks her to play dead while he turns to fire at the insurgents. Unfortunately he's quickly killed, so when a man comes closer to check on Kate, she takes out her own gun, kills the guy, and uses him as a shield to kill the others.
Then she says goodbye to Johnson before gathering as many weapons as possible and searching for a place to hide. She also tries to contact her base through the radio, to no avail. One of the insurgents is actually alive and calls for backup, so soon Kate sees trucks coming after her and decides to enter a bunker area with a sign in Russian that she can't read. The doors have chains on them and before Kate can attempt to open them, the insurgents arrive and open fire, thus she must hide to shoot back. After a few bullets are exchanged, one of the insurgents throws a missile that hits the doors and opens them, giving Kate the chance to sneak inside.
The insurgents are coming after her but the elevator isn't working, thus Kate must carefully go down a set of stairs to reach an area deep underground. Here she finds more signs in Russian and a bunch of beds, but also a row of gas masks and the body of what appears to be a scientist. On a desk, there are weird notes in Russian and a pendrive that Kate decides to take with her. The insurgents also come down and find everyday things like a mess hall, which indicates that the people that used to be here left in a hurry. Deeper into the bunker, they also find a body on a bed. Eventually they find Kate, who runs to hide while the insurgents turn on the lights, revealing a series of pods with humanoid shapes inside them. Kate takes advantage of their distraction to knock a man out and open fire with his weapon. As the insurgents fire back, one of the pods breaks and releases one of those humanoids onto the ground.
Then Kate notices the drains and escapes through there, prompting all the insurgents to follow her except for one that stays to check on the weird creature. This weird monster isn't as unconscious as it seems and when the guy turns around, the creature kills him. Another insurgent finds Kate and makes her stop while his friend goes back to find the missing man, only to find the creature feeding on the poor guy. Kate gets rid of her enemy by throwing a flare at him, then she begins climbing the stairs as she shoots anyone that tries to get in the way. One of the men grabs her ankle and Kate can't shake him off, but suddenly the monster shows up and kills the guy, allowing a terrified Kate to run away. As soon as she reaches the doors, the monster catches up and hurts her abdomen, but Kate slips away just in time to push the monster back with a few bullets and close the door with the chains.
Outside the bunker, there's an insurgent named Kabir waiting for his team, but as soon as he hears the monster, he runs away. Kate begins walking through the desert, only stopping to apply some medicine for the pain. When she reaches the road, she's hit by an American army truck, which happens to be looking for the missing pilots after seeing the crash site. Corporal Jade checks Kate to be sure she's telling the truth about her identity and steals her locket, then Sargeant Hook promises they'll take care of her. The group makes it back to the base in the morning, and Kate meets with Major Finch, the man in charge. He doesn't believe Kate's story even if Hook vouches for her but he does take the pendrive. After Kate leaves the tent, Finch calls his superiors to report unusual activity in the area, he also keeps hesitating on opening a letter. While the other soldiers bring Kabir in for interrogation, Kate approaches Jade to get her locket back. Jade denies having it and triggers a fight that doesn't stop until Hook orders Jade to return the locket.
Then, Hook explains this team is made of outcasts: Jade is a kleptomaniac, doctor Wilks used to be an addict, and Finch lost a better position because he took the heat for a mistake that Hook made. Next, Kate goes to see Wilks to get her wound checked, and Wilks admits it doesn't look like a bullet did it. Kabir's in that tent as well but when Kate asks him to back her story, he doesn't answer, apparently he can't understand her. The other soldiers wonder how there could be a bunker out there that doesn't appear on satellite images, so Kate explains it's very hidden and proceeds to use her photographic memory to write the signs she saw in Russian. Suddenly, Kabir reveals he does speak English and Russian too, and explains the sign says "don't enter".
He also finally confirms Kate's story. The other soldiers are confused because if the bunker is Soviet, then it must be around thirty years old, and nobody can survive down there without new supplies for that long. Those pods must keep the creatures in some kind of stasis. Back in the bunker, another creature breaks its pod and begins to open the door. When night falls, Everett joins Jade for the night watch while the other soldiers learn they'll be out for three-hour shifts because they're expecting trouble. Finch finally opens his letter and learns his superiors are asking him to step down. Furious, he makes a phone call and learns the higher-ups want the content of the pendrive, but he won't send it unless he gets an explanation, and hearing the truth leaves him in shock. Meanwhile, Kate and Wilks interrogate Kabir, who explains he didn't shoot anyone.
He's just a driver that was working for the insurgents to protect his family. Hook checks on his men and sends a private to relieve Everett. However as soon as he turns around, Everett hears a noise and finds the soldier gone, only having left some blood behind. Jones and Bromhead also hear a noise and as soon as they check, they notice a bunch of monsters has entered their base. The entire team immediately gets in position and opens fire while Kate wonders if the monsters somehow managed to track her. Hook informs Filch of the situation and Filch tries to make a call for backup, but the radio tower is destroyed by the monsters. The beasts are very powerful and bullets don't hurt them, so soon soldiers begin getting hurt or killed, starting with Everett. Wilks leaves the tent to offer medical attention after telling Kate to stay and watch Kabir.
Seconds later, a monster enters the medical tent and uses its very long tongue to capture Kate, but luckily Kabir finds a machete in a chest and uses it to kill the beast. Then he hands Kate a gun before running outside, but the soldiers immediately grab him to keep him guarded, thinking he was trying to escape. It isn't until the soldiers start a fire that they can finally keep these creepy things away. Wilks goes to rescue Kate and brings her to the safe spot where everyone's gathering, thus Hook takes the chance to ask for cover in order to go save Finch with Wilks. At that moment, another monster enters Finch's tent, where it ignores all the bullets to hit the major. Finch thinks he's about to die when Hook and Wilks show up and shoot the creature, this distracts it long enough for Finch to grab a bat and smash it to death. Outside, the group finds a container where they could hide, but Bromhead has to work on picking the lock because they don't have the key. When Hook and Wilks bring Finch with them, one of the monsters tries to attack them, so the soldiers open fire and Kate takes the chance to jump on it with the ax, having realized the mouth is the creature's weak spot. There are still more creatures coming, so as soon as the trio makes it back, they hide in the container and decide to wait until morning to see what happens.
The soldiers are wary of Kabir, but Kate points out he saved her life, and Kabir finally tells them what he knows. He wasn't even born when the Russians invaded, and the people in his village knew war would reach them too because a star had fallen to Earth and shook the ground. Kabir's father taught him to fight, and by 1988 Afghan forces had begun to turn the tide. His village had hope until one day people started disappearing in the middle of the night, and sometimes in the morning they would find bodies that looked like they were attacked by a bear. His father thought of hunting this animal, but as soon as the Soviets withdrew, the attacks also stopped. The village lost 46 people and Kabir's father never made it back. The next morning, the group leaves the container and discovers their friends' bodies are gone. Wilks examines a dead creature and discovers its teeth are in rows and retractable, like a shark's, and its skin is thick to function as body armor.
There's goo on the table because the creature is melting since it can't stand sunlight. Because the skin's so hard, Wilks has to use a drill to look inside, and he's shocked to discover the creature has human organs. Finch finally decides to come clean and apologizes to Kate, explaining the higher-ups have always known about the bunker. It turns out the star Kabir's people saw had been a starship, and the Soviets invaded Afghanistan just to retrieve it, the war had only been a smokescreen. The aliens were used in experiments, and the creatures are the result of combining alien DNA with human DNA. There's a whole army of them in the bunker, and last night they only sent a few to learn the team's weaknesses, so they'll likely come back tonight. Escaping isn't possible because they don't have much fuel and they would be found by the insurgents anyway. Suddenly their conversation is interrupted by the beast on the table waking up. It uses its tongue to grab Kate again, leaving her in some sort of trance while pushing away Kabir and the soldiers when they try to stop it.
Finch grabs a grenade and jumps on the beast to kill it, making this his "voluntary discharge" like the letter wanted. Afterward, the soldiers finally free Kabir's hands because seeing him fight has earned their trust. Kate feels dizzy and confesses that when the creature touched it felt like it was draining her mind, probably to learn their strategies, but she has an advantage: she knows where their nest is. Kate, Hook, Jade, Wilks, Jones, and Bromhead are all the soldiers that are left but it's enough people to bomb the bunker, and Kabir asks to go with them because he wants to avenge his father. When they arrive at the bunker, they throw the bomb inside and leave to detonate it, but Kate accidentally drops her locket and Hook returns to pick it up. This gives a monster the opportunity to grab him and bring him down into the hole. The team thinks they've lost their leader and gets ready for the detonation, but Hook suddenly contacts them through the radio to confirm he's still alive.
He doesn't want the team to go back for him and the team agrees, but Kate changes everyone's minds by pointing out that Hook would've done the same for them. Wilks stays in the truck so he can push and pull the broken elevator for the team, but as soon as they make it to the bottom of the bunker, Wilks picks up a worrisome message through the radio: there'll be a missile strike in twenty minutes, they probably got the location because of the tracker on the truck. Seeing they don't have much time, the group decides to split to cover more ground more quickly. Meanwhile Hook discovers there's a beast in the same room as him and soon he's attacked by its tongue, but he manages to distract it by biting that tongue before killing it with his knife.
Afterward, he finds all his friends' bodies and manages to take some weapons from them. As the team searches for Hook, Kabir finds the bodies on the tables and realizes these are the missing people from his village, who probably were the ones that became creatures later. Kate finds a pod on the wall she didn't see before, and when she turns on the light, she discovers the original alien floating around still alive. At that moment, Hook leaves the room and asks Kate for directions through the radio, only to be intercepted by another monster.
He runs fast enough and manages to join his team to kill the beast together by shooting at its head, but this leaves many of them without ammunition. Meanwhile outside, Wilks suddenly finds himself surrounded by insurgents, meaning he has to open fire and defend the entrance on his own. In the bunker, the creatures are hatching out of the pods, and Kate comes to the conclusion they knew they were coming because they read her mind. The team runs out of the pod room and closes the door, but the creatures keep hitting it with outstanding strength, so Jones stays behind to hold the door to give the team the chance to escape. As they run down the corridor, Jade hears a noise indicating a monster is coming, so she stays behind too to fight it and protect the team.
As soon as the group reaches the elevator, they realize Jade's gone, and Hook decides to go back for her after telling the team to leave if he isn't back in two minutes. Jade takes the beast into the mess hall and after exchanging a few hits she manages to defeat it, only for a second one to appear behind her. By the time Hook arrives, it's too late: the beast has killed Jade. Hook begins fighting the creature with any tools he can find around, meanwhile Jones realizes he can't hold the door anymore and lets go of it before detonating the bomb to bring everyone down with him. Hook hears the explosion and hides inside the fridge right before the flames enter the room, killing the beast there too. At the elevator, more monsters are coming and the team is running out of bullets, so Bromhead starts calling for Wilks to pull them up.
Wilks is still fighting the insurgents, who are now getting inside the truck to fight him hand-to-hand. Kate, Bromhead, and Kabir also hear the explosion and hide in the elevator for safety at the same that Wilks finally kills the enemy and activates the truck. Unfortunately the elevator is too heavy and it pulls the truck down with it, but Wilks can't stop it because more insurgents are arriving and opening fire on him. More creatures arrive at the elevator, and Kate and Kabir can defend themselves with the ax and the machete, but Bromhead only has his fists and gets killed. The truck outside keeps advancing, so Wilks has to move out of the way and see it fall. Kabir sees the truck coming and tells Kate to get out of the elevator while he keeps the creatures distracted, thus when the truck finally crashes, he dies together with all the monsters. Wilks is captured by the insurgents while Hook returns to Kate's side as a monster follows him. Together both soldiers grab onto the elevator's wires, which quickly take them back up with a quick shot from Hook. As soon as they make it back outside, Kate and Hook shoot the insurgents, saving Wilks right before he gets killed. At that moment, a plane appears in the sky and drops a missile, so the trio pushes a man out of a car and steals the vehicle to escape the area. The explosion doesn't reach them, although it does push the vehicle off the road, and Kate's sure this bombing came from the government to get rid of the evidence.
Her theory is correct because at that moment, special agents land on the base to look for any beast bodies, but they leave when they only find Finch's. Kate isn't worried though because she reveals she has the pendrive with all the intel, a gift from Jade after she used her thievery to take it from Finch. Now they only need to make their vehicle work again.