It's a normal day in Colombia, and a group of workers is arriving at Belko, a nonprofit
organization that helps South American companies hire US-national workers. This morning everyone is
surprised because instead of the usual security guard at the entrance, there are armed soldiers
inspecting everyone before they're allowed to get in, asking for IDs and checking trunks. Boss
Barry notices certain employees are sent home and when he asks a soldier about it, his question is
ignored. Inside, everyone is going through their mornings as usual, although they do notice only
the foreigners were allowed to stay and all the Colombians were sent home. Today is Dany's first
day on the job and executive Vince teaches her the basics, he also makes sure Dany has already had a
tracker implanted in her head. All employees are put through this because kidnapping is a serious
problem in Colombia and the tracker helps the company protect their employees. While Marty hides
in the bathroom to smoke, Leandra has to deal with constant harassment from Dukes, who stares
at Leandra while she works and won't stop when she tells him he's making her uncomfortable. At
least she can find a distraction in her boyfriend Mike, who also works here and they often put down
the blinds to make up during work hours. Today they almost get caught, so Mike goes back to his
own office. When he looks through the window, he notices one of the soldiers entering a hangar next
to the company building. Curious, Mike calls Evan, the security guard in charge of the reception, but
he doesn't know what the deal with the soldiers is either. Suddenly, an unknown voice begins talking
through the intercom and announces that there are eighty employees in the building, but in eight
hours most of them will be dead unless they follow his orders. The first task the voice gives them is
to murder two people within the next half hour. If there aren't two bodies in thirty minutes,
there'll be serious consequences. Employees are confused by the message and think it's some sort
of prank, but they still leave their desks to find out what's going on. A woman tries to get out,
but at that moment the building's security measures activate and metal plates begin
blocking all the windows and exits, this also blocks all internet and phone signals. The
air conditioner shuts down as well. Vince goes to check the control room and finds it empty,
so the voice somehow reached them from outside. Everyone rushes to the lobby to demand answers,
but Evan doesn't know what's happening either, and there's no way to call for help. People are
starting to panic, feeling like they're trapped in a dungeon with no sunlight. Mike asks maintenance
men Bud and Lonny to use their blowtorch to make a hole in the metal plates, and they agree to try.
Barry tries to calm everyone down by explaining the metal plates are a security measure the
company installed because they're a government building and they needed protection in case of a
military event. It seems some hacker discovered this feature and is playing a prank on them,
so they need to wait patiently to avoid any accidents. Some people go to the roof to have some
fresh air and find Marty with his friend smoking to forget about their nerves. Since the building
is in the middle of nowhere, there's nobody they can yell at for help. In the lobby, Bud and Lonny
try to melt the metal plate to no avail. The plate isn't even getting hot, which means it isn't any
kind of metal they've ever heard of. Mike tells Barry that he's worried this may be actually
serious because it can't be a coincidence that the soldiers took over security in the morning,
but Barry just tells him he's being paranoid. Up on the rooftop, the group notices a guard in
a sentry box near the hangar and tries to get his attention, but the guard just gives them a
weird look and continues to drink his tea. Marty thinks everyone is worrying too much because this
is obviously a psychological test to see how the workers would react in tense situations. Suddenly
one of the employees screams and falls dead to the floor. At first it looks like a bullet wound, but
soon three more people die in the lobby too, all of them having the same issue: something suddenly
hurting the back of their heads, but there aren't bullets anywhere. People scream and panic as they
run away to hide, but Barry notices something weird and approaches one of the bodies to discover
the heads exploded because of the tracker the company implanted in them. Mike immediately runs
to find a knife and takes it to the bathroom to try to remove the tracker in his head, but at that
moment the voice speaks again and tells him to stop or his tracker will explode in ten seconds.
Mike doesn't give up until the last second, and then lets a secretary give him stitches. Leandra
goes to the kitchen to find some ice for Mike and Dukes follows her to keep on harassing her,
apparently he thinks that a coworker treating him with good manners equals "sending mixed messages".
Leandra insults him and walks away. Meanwhile in another room, some employees discover there have
been cameras hidden everywhere all along. Barry approaches Evan to ask him for the keys to the
armory where the guards keep their guns, but Evan refuses because he thinks it'll make everything
worse even if Barry swears it's "just in case". When Barry reminds him that he's the boss, Evan
simply quits. Meanwhile Bud gives Lonny a wrench and asks him to watch his back before they go to
the basement to check on the power and see if they can at least bring back the air conditioner. At
that moment the mysterious voice speaks again, saying he hopes everyone can tell the game is
serious now. He reminds them not to touch the cameras or to remove the tracker, otherwise he'll
make anyone that tries explode on the spot. There are seventy-six employees left, so the voice gives
them the next task: they must murder thirty people in two hours, or he'll kill sixty as punishment.
Everyone in the lobby begins panicking and arguing over what to do, some guys even go to the kitchen
to find knives. Marty turns on the fire alarm thinking it may alert the fire department,
but it's actually a self-enclosed system, so Evans looks for a way to turn it off. In the basement,
Lonny begins crying and loses it when he hears the alarm. Bud tries to comfort him, but Lonny's
too anxious and paranoid and thinks Bud wants to kill him, and he responds by hitting him with the
wrench. Bud quickly dies. As Lonny cries with guilt, he notices Dany has seen everything, and
although Dany swears she won't say anything, Lonny goes after her to attack her. Dany tries to push
him away from her and Lonny accidentally hits his head against some small metal bars that instantly
kills him. Upstairs, Barry uses his power as a boss to make everyone sit down and discuss things.
Opinions are divided: a group supports Mike when he mentions there shouldn't be any killings,
but the other half supports Barry when he points out they don't want to kill but it's the only
choice they have. Leandra interrupts the argument by offering an idea: they could make banners and
hang them on the roof to see if any passing cars will stop. Most people agree and leave with her,
but Barry recruits Dukes, Terry, and a few others for an alternate plan. Mike, Leandra,
and Evans are gathering supplies to make the banners when they suddenly hear a weird sound.
It turns out Barry and his group are using the blowtorch to try to gain access to the armory.
The trio tries to make them stop and they won't listen, so Evans takes out his gun to threaten
them. Mike immediately calms him down to avoid violence, but he uses the gun to destroy the
blowtorch tank. Afterard the trio goes upstairs to work with the others. When the banners are ready,
the group goes to the roof and tries to hang them, but this only causes the soldiers to shoot at them
to make them back away, and one of the employees gets his hand hurt. Mike wants to try again,
but at that moment the voice announces that anyone who keeps insisting on hanging the banners will
get their tracker detonated. Mike doesn't listen and the group has to drag him back by force. They
give up and decide to go back inside. As they make their way downstairs, Mike wonders if the
government is behind all this. The job has always been strange, nobody never put much attention to
how much they worked, and the building is in the middle of nowhere, almost as if it was
always designed specifically for this. Suddenly they're ambushed by Barry and his men, who push
Mike down the stairs and demand to have the armory keys. Evan throws the keys to a lower floor, and
Dukes reacts by killing him with a knife. Leandra calls Dukes out for the unnecessary violence and
Dukes almost kills as well, he only stops because Barry makes everyone move on. Afterward, Barry's
group retrieves the keys and opens the armory to get all the guns that only they get to use. They
search for every person hiding in the building and bring them to the lobby at gunpoint, one guy
sees Dany hiding in the basement but thankfully he keeps his mouth shut. Mike wakes up on the stairs
and finds Evan's body, but Dukes finds him as well and makes him come along. In the lobby, everyone
is upset and on the verge of a panic attack, and Barry keeps things under control by shooting at
the ceiling. He ignores any offers of bribes and people's personal reasons why they should live,
like taking care of elderly parents. Instead Barry comes up with his rules, and he starts by saving
those who have kids that are under eighteen. Then he gathers every employee that is over the age
of sixty, but this isn't enough, so he begins choosing people at random, although obviously
he picks Mike out of spite. Anyone that tries to resist gets shot on the spot. Not wanting to
hear his victim's suffering, Barry orders his men to turn on the radio so the music can cover the
screaming as he begins to shoot the chosen ones one by one. Dany hears the commotion and comes
to see what's going on, discovering the massacre. She immediately runs back into the basement and
shuts down the power, leaving the entire building in darkness. People begin to yell and run while
Barry and his men shoot at random, killing several more people. Many employees run to the basement,
and Dany finds Roberto in the elevator, who asks her to team up to see if they can escape through
the elevator shaft. Chaos and panic take over the place as people continue to die. Suddenly the
voice announces twenty-nine people have died, so they have to kill one more in the next two minutes
if they don't want thirty more to die. Leandra manages to find an empty office and takes the
blade from a paper guillotine to defend herself. She can hear Terry coming, so she hides under a
table after putting her shoe around a corner as bait. As soon as Terry walks by, Leandra hits
him on the leg and makes him drop his gun. Then she gets ready to kill him, but Terry begs for
his life and Leandra decides to spare him. At that moment the voice announces they timed out without
finishing the task, so thirty-one people will have to die. Leandra's decision turns out to be useless
because Terry dies on the spot, and thirty more employees all over the building soon follow him.
Once the thirty-one deaths are reached, the voice announces the final stage of the game: in one
hour, whoever has killed the most people will be allowed to live. Then he shares the current tally:
Barry has eleven, Dukes has seven, and Vince and Dany have one each. Barry's group immediately
continues to hunt people down to add more kills to their tally. A secretary tries to convince
Barry not to kill her by offering herself, but Barry kills her anyway before entering
the elevator where Dany and Roberto are hiding. When Barry presses a button, Dany panics and
jumps off the elevator roof into the shaft edge, but Roberto doesn't react quickly enough and is
crushed. This causes the elevator to get stuck, leaving Barry trapped inside. Meanwhile Leandra
grabs Terry's gun and goes downstairs, where she finds Marty and his friend collecting the
trackers from the people that died at the hands of others. Since these trackers have explosives,
they may be able to put enough of them together to blow up the wall. Then Leandra uses the intercom
to let Mike know she's on the first floor and asks him to join her. Mike immediately takes
the stairs and comes across a cafeteria lady, so he brings her with him. Marty, his friend,
and Leandra go to the cafeteria and find Dukes murdering another employee with extra violence,
almost as if he enjoys it. Leandra shoots him but the bullet lands in his leg, and Dukes fires back,
killing Marty and his friend. Using a table for cover, Leandra grabs an axe and after tossing the
table on top of Dukes to capture him, she uses the axe to hit him repeatedly. In the elevator, Barry
grabs the handrail to force the door open while Dany carefully makes her way through the shafts
until she makes it back to the elevator. Leandra returns to the lobby and reunites with Mike, where
she shows him the explosives Marty collected and Mike puts them in his pocket. Suddenly Vince shows
up with a molotov cocktail and kills the cafeteria lady. Mike and Leandra begin running away and
come across Barry, who opens fire on them. Vince also tries to chase them with more bombs in hand,
but Barry finds him first and kills him, giving Mike and Leandra time to hide. Dany manages to get
inside the elevator, but when she reaches another floor, Barry shoots her as soon as the doors open.
Meanwhile Mike discovers Leandra was reached by a bullet. Mike swears he'll get her out and get
help, but Leandra tells him she loves him before she dies. The grief and rage building in Mike are
so strong that when Barry enters the room, Mike leaves his hiding spot to attack him. A fierce
hand-to-hand fight begins between them, and Mike manages to win it by killing Barry with a tape
dispenser. Mike begins crying because he hates he had to resort to this, and at that moment,
the voice announces he won. The windows and doors open, and two soldiers come to pick Mike up to
take him to the neighboring hangar. There Mike meets the man behind the voice and his partners,
who explain they belong to an international organization run by the greatest thinkers in the
world. They created their company to study human behavior unfettered by conventional concepts,
however they refuse to explain what the experiment is actually about and they begin to ask Mike how
everything has made him feel. Mike refuses to answer and notices a panel with everyone's names
next to a switch, which was used to activate the trackers. It's then revealed that when Mike was
grabbed by the soldiers, he put the explosives Marty gathered inside a soldier's clothes,
so he runs to the panel and activates all the switches except his own. The soldiers die, then
Mike takes their weapons and uses them to kill the so-called scientists. Afterward Mike leaves
the building, thinking it's over now. However a series of screens reveal they're recording the
winners of dozens of games like this, and a new voice announces it's time to start Stage Two.