Lia frantically attempts to call the authorities on her phone, but there is no signal. Suddenly, she hears a chorus of screams echoing throughout the neighborhood, and upon glancing outside, she witnesses a horde of rampaging zombies causing chaos. Gripped by fear, Lia accidentally drops her phone, and at that moment, the back door of her house creaks open. Determined to investigate, Lia cautiously approaches the door, only to find a wounded man seated, clutching his bleeding arm. Pleading for assistance, the man requests cloth to staunch the bleeding. Curious about his injury, Lia inquires about its cause, to which the man responds that it was a cut and not a bite. Before Lia can react, the zombies relentlessly pound on the back door.
Reacting swiftly, the man rises and ventures further into the house. Lia sternly instructs him to leave, but he pleads for her help, emphasizing his desperate need. As the zombies make headway, breaking down the door partially, Lia races upstairs, while the man attempts to follow. However, Lia restrains him and reiterates her demand for him to vacate her house. The man beseeches Lia for hospitality, but Conor, who stands behind Lia, observes the man's wound and realizes it's a bite mark. Lia, filled with apprehension, warns the man once again to stay away. The man gazes at his bite wound, his right eye gradually turning gray. Overwhelmed with fear, Lia insists that he back off.
Meanwhile, the veins on the man's arms bulge intensely, causing him to panic. He makes a desperate attempt to ascend the stairs, but Conor aims his bow with an arrow pointed directly at the man. Despite the man's plea to avoid being left outside to die, Conor swiftly releases the arrow, piercing the man's chest. Caught off guard, the man tumbles down the stairs. The zombies break into the house, and in their frenzy, they sink their teeth into the fallen man. Conor witnesses the man's agonizing screams as he reaches out towards him. Lia grabs Conor, guiding him to Leona's room, where they seek refuge.
In the workplace drive way next to the parking lot, Sam sits inside his car, engaged in a phone call with someone, expressing how enjoyable his night was. Suddenly, another vehicle crashes into the back of Sam's car. Abruptly ending the call, Sam mutters to himself, questioning who could be foolish enough to crash the new boss's car. Fuming with anger, he steps out of his vehicle and approaches the car that hit him, only to be greeted by a horrifying sight—a zombie gnawing on the driver. Recoiling in shock, Sam watches as the zombie turns its attention toward him and violently smashes its head against the shattered windshield. Emerging from the broken glass, the zombie gives chase to Sam, who seeks refuge inside the factory and secures the door behind him. Relieved for a moment, he attempts to call the police, but his respite is short-lived when a wounded man appears behind him, urging Sam that they cannot stay there.
As Sam turns to face the man, he notices a zombie rapidly approaching. Reacting quickly, Sam uses the wounded man as a shield, sacrificing him to the zombie's bite. Seizing the opportunity, Sam flees. Meanwhile, on the work floor, Adam and Kiren find themselves backed against a wall. Kiren, trembling with fear, sits on the ground, using his legs to prop up a table as a shield, while Adam fends off numerous encroaching zombies, striking at their heads. Aware that Kiren's cries are attracting more zombies, Adam continues his assault with a hammer. In the midst of the chaos, Adam reminds Kiren of something he once said to him when they first met. Slowly recalling the moment, Kiren remembers claiming to be really sick and that he said he was a hero and asserting that heroes never die. Fueled by determination, Adam implores Kiren to rise and save him. Overwhelmed by fear, Kiren questions what kind of hero fights zombies.
As a dozen zombies converge upon them, Adam seizes the table with his arms and uses it to block their advance. Addressing Kiren, Adam declares that they will the first zombie heroes, with urgency, he implores Kiren to join him in pushing against the table, thwarting the zombies' attempts to reach them. Exerting all their strength, they successfully repel the undead horde. Adam then urges Kiren to run, fueled by adrenaline Kiren outpaces Adam. Running past infected workers, Kiren leaps over a transforming zombie, with another charging at him from the side. Petrified, Kiren instinctively shields his face with his arms, but Adam intervenes, striking the zombie away with his hammer, instructing Kiren to keep moving. Pressing forward, Kiren approaches a door and is about to press the button to open it, only to witness a man on the other side being attacked by zombies. Overwhelmed with fear, Kiren collapses, succumbing to tears and longing for his parents. Sensing his distress, Adam rushes to Kiren's side, encouraging him not to give up. Adam declares his intention to open the door and eliminate the approaching zombies, suggesting they make a break for the QC room. With resolve, Adam activates the button, causing the door to open. Engaging the zombies head-on, Adam dispatches one by striking its skull downward, then repels another with an upward blow, allowing him to retrieve Kiren and lead him out of the work floor.
Navigating the loading area, they eventually reach the storage area, filled with towering heavy-duty pallet racks. Adam comes to a sudden halt to see many zombies charging at them, he then strikes a rack with his hammer and kicking it repeatedly until it collapses. Seizing the opportunity, they resume their escape, narrowly avoiding being crushed by the cascading racks, which eliminate the pursuing zombies. They barely escapes the storage room from the collapsing racks. Gazing upward, Adam spots Sam struggling to unlock the QC room door, accompanied by a few other workers. Assisting Sam, they all seek refuge inside the room, quickly securing the door. Adam and some of the workers begin barricading the entrance. Amidst the chaos, one worker breaks down, sobbing uncontrollably. Sam kicks him to silence him, though Adam intervenes to prevent further harm. However, they soon notice the bite mark on the worker's arm. In a state of desperation, the worker insists he doesn't want to die and claims to be okay. Their fears amplified, everyone witnesses the worker's eyes beginning to bleed, as he frantically wipes them in terror. Reacting decisively, Sam seizes Adam's hammer and smashes the worker's skull to pieces. A female worker screams, accusing Sam of murder, but he vehemently argues back, asserting that she's delusional and that the real killers are outside. Adam calms the group and emphasizes the need to refocus and devise an escape plan. Despite Sam's concerns about the dire situation outside, Adam assures them that they will formulate a plan for the exterior as well, urging everyone to rest and allow the situation to settle momentarily.
Moments later, everyone gathers in the QC room and begins to consume the remaining food from the fridge. Adam then proposes that they head to the security room to check the cameras and devise a safe escape plan. While Adam suggests this, Sam remains engrossed in his phone, hoping for a signal and worrying about the safety of his family. Adam takes out his phone, gazes at a photo of his family, and expresses confidence that Conor can protect them until he joins them. Suddenly, everyone's phones regain service, and they frantically call their families. Sam quickly contacts someone and anxiously inquires about their well-being. Adam observes the emotional reactions of those around him. Kiren struggles to reach his parents and asks Adam if he plans to call his family. Adam nods and dials Lia's number but is unable to connect, receiving a message stating that "Lia is on another call." Adam hangs up without dwelling on it, as Kiren's phone starts receiving an influx of messages. Surprised, Kiren checks his phone. The phone service goes offline again, prompting Sam to vent his frustration by kicking a chair and promising to return home soon. Adam notices Kiren's shocked state and is shown a message from other factory coworkers on Kiren's phone. Adam reads the text, revealing that nine individuals are trapped in the cafeteria room of the Red Zone, and six are stuck in the Green Zone bathroom. Sam whispers to Adam, suggesting that they escape the factory alone and head to his place. Adam brushes off Sam's plan, asserting that the more people they gather, the better their chances will be. Sam comprehends Adam's perspective and asks who wants to join them. However, no one responds. Sam privately approaches Adam and suggests that they use the others. Adam dismisses Sam's plan and declares that he has a strategy to save everyone. He instructs everyone to stay put, assuring them that they will return. Adam then informs Sam that they will first proceed to the Green Zone, followed by the security room, which is closer, and then the Red Zone. Sam agrees, and they leave the QC room.
Sneaking around, Sam and Adam make their way to the Green Zone. Sam retains his grip on the hammer, while Adam grabs a nearby wrench. During their journey, Sam tells Adam that he doesn't need to be a hero and save everyone. Adam responds by emphasizing that the lives of their coworkers are in their hands, and he cannot bear the thought of not being able to save anyone of them. Sam argues that living and reuniting with family is preferable to dying with coworkers. Suddenly, a zombie spots them and gives chase. They sprint away, and more zombies join the pursuit. In a desperate move, Adam pulls the fire alarm, diverting numerous zombies throughout the factory. They push a rack, causing it to topple onto the pursuing zombies. They quickly reach the storage room and knock on the door. However, the door bangs back, leading Adam to assume that there are only zombies on the other side. They proceed to the office, but a worker speeds past them on a forklift. They then witness a horde of zombies approaching down the hallway. Seeking refuge, they enter the office and hide while the worker crashes the forklift into the front doors, inadvertently allowing the horde to reach him and inflict bites. Sam watches in horror, and Adam notices a zombie approaching Sam. Adam strikes the zombie with his wrench, repeatedly smashing its head until the wrench becomes stuck. A zombie lunges at Sam, and Adam rushes to his aid but is attacked by another zombie. They both fall to the floor, fending off the zombies atop them. Adam spots the hammer near Sam's feet and instructs Sam to "Give me the hammer!". Sam kicks the hammer, sliding it into Adam's hand. Adam smashes the zombie's head with the hammer and swiftly dispatches the one on top of Sam. Sam recognizes the security guard-turned-zombie and searches his body for keys. They proceed to the camera room, where they are shocked to witness multiple zombies throughout the factory but relieved to see the people in the Red Zone cafeteria room are safe. Adam presses a button, silencing the fire alarm. He decides to activate the speakers in the Green Zone, using his voice to lure the zombies away. Adam addresses the zombies through the microphone, causing most of them to converge on the sound in the Green Zone. While observing the cameras, Adam notices Kiren walking down the hallway in tears. He communicates through the mic, instructing Kiren to hide momentarily. Kiren follows the instruction, and many zombies enter the Green Zone. Kiren emerges from hiding and heads to the security room. There, he explains to Adam that when the fire alarm sounded, everyone panic in the QC room, leading some individuals to leave, allowing the zombies to enter. Kiren, barely escaping the QC room, is comforted by Adam, who advises him to remain in the camera room to distract the zombies in the Green Zone. Kiren mentions that someone is still hiding in the QC room's locker. Adam nods, expressing his intention to rescue her and assigning Sam the task of saving the others in the Red Zone.
Adam and Sam separate and proceed accordingly. Adam arrives at the QC room, where he encounters a couple of zombies trapped in the doorway. He eliminates them and enters the room, dispatching two more zombies. Opening a locker, Adam finds a worker who embraces him with relief. Meanwhile, Kiren watches Sam through the cameras as he blocks the cafeteria room door in the Red Zone with shelves and chairs. Kiren repeatedly questions Sam's actions, but Sam looks up at the camera, placing a finger on his lips to signal Kiren to remain quiet. Sam proceeds to the machinery, overworking the machines through the system. Adam tackles Sam and demands an explanation for his actions. Sam reveals that it was all a distraction for the zombies and with the door blockade serving as a diversion for Adam. Although Adam is on the verge of punching Sam, his attention is diverted by a machine catching on fire. Sam urges him to hurry, warning that everyone will die otherwise. Adam rushes back to the cafeteria room, where the lady worker struggles to remove the rack blocking the door. Kiren watches through the cameras, witnessing the panic among the people inside the cafeteria room, and begins to cry at the dreadful sight. Adam opens the door, only to discover that everyone inside has committed suicide by hanging themselves. The lady worker enters and collapses to her knees, lamenting that one of them was her sister. As explosions erupt in the Red Zone, Adam tells the lady worker that they must leave. However, she refuses, unwilling to abandon her sister. Adam, torn by the decision, is unable to choose a course of action.
Sam opens the trailer door leading outside from the Red Zone and dashes to the front of the factory, taking cover as a massive explosion occurs from the Red Zone, attracting zombies toward it. Sam emerges from hiding and gets into his car. As Sam tries to exit the parking lot in his car, a zombie creature resembling a frog leaps onto his vehicle, causing significant damage to the front. Sam observes the bizarre Zombie Frog, noticing its humanoid frog body composed of human parts. The Frog opens its large mouth and extends its tongue through the windshield with great force. Sam narrowly avoids being caught by the tongue and quickly exits the car, intending to flee. However, the Frog strikes again, this time hitting Sam's back and pulling him towards its mouth. Sam struggles to free himself from the tongue's grip, desperately resisting being swallowed by the Frog. With one hand, Sam reaches into his pocket and retrieves his phone, throwing it into the Frog's enormous eye, causing it pain. Seizing the opportunity, Sam uses both hands to tear his shirt to get away from the tongue's grasp. The Frog jumps away, leaving Sam to survey the parking lot for available vehicles to steal. He forcefully opens a car's trunk and retrieves a screwdriver. He heads towards the driver's side, preparing to break the window with the tool. However, Adam suddenly lunges at Sam, tackling him to the ground and throwing punches. Emotionally charged, Adam expresses his unforgiving sentiments towards Sam. He proceeds to strangle Sam, but then experiences a momentary mental struggle as a voice urges him to go ahead and kill Sam. Adam clutches his head in pain, but Sam interjects, reminding him of the urgency to reach their families as quickly as possible. Adam notices the desperation in Sam's eyes and notices a horde of zombies approaching them. Swiftly, Adam lifts Sam up, and Sam inquires about Adam's car. Adam points towards his vehicle, and they both sprint towards it. Glancing back, Sam sees hundreds of zombies chasing them through the parking lot. Adam retrieves his keys, but suddenly feels a sharp pain in his thigh, realizing a screwdriver has impaled him. Falling to the ground, Adam rolls onto the pavement and sees Sam picking up his keys. Adam struggles to crawl towards his car. In frustration, Adam angrily calls out Sam's name as Sam drives away, witnessing Adam being overwhelmed by the relentless horde of zombies. Adam's eyes fill with rage as his body is torn apart by the onslaught of zombie mouths. He closes his eyes and succumbs to death. Meanwhile, Kiren watches the tragic scene unfold from the camera room, tears streaming down his face. He curls up in the corner, overwhelmed by fear and repeatedly reassuring himself that he is not a hero.