At the beginning of the film, we are shown the state of the city during the zombie attack, which is referred to as Rotter in this film. It is not known what caused this tragedy to take place. A woman is seen being chased by Rotter and running with her clothes ripped off.
The scene then shifts to four hours prior to the incident. In a morgue at the University of Whittendale, several medical students are being tested by their lecturers to determine the cause of the patient's mysterious death. They are Zoe, Abby, Peter, Suzy, John, and Doctor Beeman.
After finishing the test, Zoe goes straight to the lab to complete research on blood samples. Doctor Beeman approaches her and asks her to take a sample of Max's blood, a patient who has extremely high antibodies when compared to normal humans. DrBeeman says this is a great research opportunity for Zoe's final project.
After that, Zoe goes to see the patient that Doctor Beeman had mentioned. We can clearly sees Zoe doesn't like Max, because he is so desperate to win her affections. In fact, Zoe is forced to meet him is just because of Max's blood sample is different from the others.
Max shows that he truly desires her affection by engraving Zoe's name on his arm. Fortunately, when Max is just about to begin his sexual assault, Abby comes at the right time and chases him away. Abby then invites Zoe to their end-of-semester celebration, which will be held on their university.
They also keep 2 kegs of beer in the morgue earlier, where Peter and Zoe are told to go get them. Peter is damn annoying in this scene. After picking up the keg of his drink, Peter immediately leaves Zoe behind.
However, just as Zoe is about to walk out the door, Max bursts in and launches a sexual assault against her. But this time his attack is failed again, because the body they were investigating earlier suddenly wakes up and attacks Max right away. Zoe runs away as soon as she notices this, and go to the party room and tell her friends about it.
But before they have a chance to do anything, they are attacked by Doctor Beeman, who has turned into a zombie. Followed by zombie corpse who comes to pounce on Peter. When the zombies are attacking everyone, Zoe has enough time to save escape through the window.
Unfortunately, her friend Abby, can't be saved because she is attacked by several zombies. The incident that happened earlier explains the causes of the zombie attack in the city. The film then jumps forward five years to a time when the virus has already spread throughout the world.
The remaining humans are housed in a military-run bunker in the mountains. Zoe, is the only doctor left is assigned to the High Rock Emergency Bunker, a military surveillance and observation station. She's working to find a vaccine for the virus and assisted by Elyse.
They have lost contact with the rest of the bunkers in the last year, and they are forced to fend for themselves here. While she is conducting her research, a mother named Wendy approaches her and reports that her daughter, Lily, is suffering from a high fever and has not recovered. When Zoe checks on Lily's condition, she becomes worried when the antibiotics she gave have no effect on her.
Therefore, Zoe rushes to meet Lieutenant Miguel, the bunker's commanding officer, who is currently holding a meeting. Zoe then goes into detail about Lily's condition, which is pneumonia. In other word, if she is not treated immediately, her life will not be saved.
Zoe asks Miguel to allow them to go to her old medical lab at her university, in order to obtain the right antibiotics for Lily's treatment. But Miguel firmly refuses, stating that it could threaten the life of his team. Moreover, Zoe's old university is outside of the range in which they can pass.
But due to the risk of infection from Lily, Lt. Miguel has no choice but to agree with Zoe's plan. The following day, Miguel sends his team, which is led by Baca, Zoe's boyfriend.
Their squad consists of Lucy, Frank, Alphonse, Elyse, Derek, and Thomas, there are assigned to escort Zoe. Halfway through their journey, their car suddenly breaks down, forcing them to stop and fix it. It appears that the state of the forest is so tense and potentially dangerous if they continue to remain there.
When night falls, all of them start to panic when they're still unable to fix the vehicle. They are soon approached by the creatures they don't want to deal with. Luckily, Lucy is able to repair their vehicle just in time.
Once they arrive at the university, Baca divides his team into two groups. There are no problems on their way to the medical room, and they manage to take their medicine without any difficulty. And, even on the way back, they don't seem to encounter any major difficulties.
However, the problems starts when Zoe suddenly decides to go into her research room first, to get some of her research materials. Not long after, Zoe is being pursued by a zombie, and it turns out to be Max. The sound of the gunshots causes Baca and his squad to realize that Zoe is not with them.
Meanwhile, the Rotters are moving in the direction of the gunshot as well. Luckily, Baca has arrive first before the Rotters. In their attempt to escape from there, Frank does not survive because he is getting bitten by Rotter.
As a result, they are forced to leave Frank with the zombies. Well, when Zoe runs away from Max's pursuit earlier, she accidentally dropped her hair tie. Long story short, they make it back to the bunker.
When Lieutenant Miguel learns of Frank's death, he becomes enraged and blames Zoe for her plan. Elle also comes up to them and asks about Frank. When they have an argument, they don't realize that they will dealing with a much more big problem.
This is due to the fact that they already brought a zombie Max who is secretly riding under their car. As a result, this handsome zombie manages to get into the bunker as well, He then sneaks through the air vents in an attempt to find Zoe's room. Zoe is in Lily's room when he finally manages to track her down.
When Zoe exits the room and begins walking alone, she is startled by Max who chases her down the hallway. Zoe has had enough time to set the alarm, so Bacca, Alphonse, and Lucy rush towards her. Zoe is finally cornered, but it seems that Max doesn't want to bite her.
Bacca and her friends then arrive and immediately shoots Max. When Zoe realizes that Max can be used in her future experiment, she asks her friends to restrain him. When Lieutenant Miguel gets to know about this, he doesn't agree with their actions and wants to shoot him straight away.
But Zoe stops him because this zombie is still conscious. Elle then comes and asks Miguel to give Zoe a chance to do her research. After a few days, Zoe discovers the fact that zombie Max still has several functional organs such as the heart, brain, and the others.
Zoe then attempts to take a blood sample and she has no choice but have to deal with Max's disgusting actions. Shortly after, Baca comes into the room and Zoe explains that she found a special hormone in Max's blood, which can stop the spread of the virus. In other words, the blood can be used as a vaccine if the conditions are met.
Therefore, Zoe requests that live virus samples be taken from several Rotters who are still alive in examine the differences. Baca is a little worries about her plan, especially in light of the death of his friend just a few days before. But Zoe continues to persuade Bacca, until he finally agrees.
They wait until it's dark, before they do their mission without Miguel's knowledge. Everything goes smoothly at first, and Zoe even manages to obtain a blood sample. Unfortunately, they are unable to withstand the gate because of the increasing number of Rotters who're trying to get in.
Elyse is bitten by the zombie, and they are also forced to leave Thomas who has already been surrounded by the Rotters. Miguel, who has just realized this is outraged with all of them. Miguel vented his rage on Zoe, stating that her idea will undoubtedly result in a reduction in the number of his team.
Miguel then points his gun at Elyse who has been bitten, and instantly kills her on the spot. He threatens to kill Max within 12 hours no matter what happens. Baca, who doesn't agree with Miguel's actions, immediately reprimands Miguel in his room.
Baca says this is a sacrifice that must be made for humans to survive in the future. But Miguel believes Zoe is hiding something after discovering her name tattooed on Max's hand. Following his disappointment, Baca directly asks Zoe about it, and confirms if she can actually make the vaccine.
Zoe claims that Max is nothing more than a lecherous man who has a sexual interest for her. Of course, if Zoe doesn't need Max for her research, she'll kill a guy like that. As Zoe continues her research, Alphonse and Lucy come to calm her down.
At this point, Lucy makes the mistake of approaching Max and taunting him, which makes him angry. He manages to get the key to the handcuffs on Alphonse's pants without anyone noticing. As Zoe continues her research on her own, she is finally able to confirm that Max's blood can be used as a vaccine for those who have been infected with the virus.
But Max is already free of his shackles and immediately strangles Zoe. Luckily, Zoe manages to douse him with ammonia, before managing to escape. Once they return to check the room, it turns out that Max has already disappeared, turning the situation into an emergency once more.
They try to find Max and order everyone in the bunker to gather in the hall. Lily, on the other hand, has start to recover after taking Zoe's medicine, and now able to walk on her own. Unfortunately, she bumb into his mother, who has turned into a Rotter.
While Lily is trying to run away from her mother, Max suddenly appears and kill her mother before kidnapping Lily. Not long after, Zoe finally manages to find Lily who is being held hostage by Max. Max explains his purpose for comes here is to get Zoe out of there.
As a result, Zoe must follow his orders in order for the child to be saved. After that, Max opens the gate. But when the Rotters arrive, they try to bite Zoe, causing Max to struggle in protecting her.
When Miguel and the team get there, they have to fight the Rotters who have already invaded. Miguel's shot hits Max but Zoe instead runs out when she notices Lily running out the gate. Plus, Max sees them running outside and chases after them.
Zoe is able to catch up with Lily, and they hide in a greenhouse. However, their presence is noticed by Max. After struggling to survive, Zoe finally manages to kill Max.
Meanwhile, the Rotters' attacks are getting worse and Baca get bitten by one of the Rotters. Miguel finally decides to close the gate because there are too many Rotters coming in. Of course Baca doesn't agree with this, because he is worried about Zoe and Lily.
While they are arguing, Rotter appears out of nowhere and attacks Miguel, eventually killing him. Baca still can survive of the attack. Lucy, on the other hand, is forced to die at the hands of Alphones after being bitten by a zombie.
Finally, Baca decides to reopen the gate. But because he has been infected, he starts to feel hopeless, and attempts to end his life. Zoe shows up at the right time and convinces Baca that she is capable of curing him.
Zoe then treats Baca, making him the first human to be treated with her artificial vaccine, and she is successful in curing the virus. At the end of the film, it appears that the humans who are still surviving are beginning to experience the peacefulness of life. Every single one of them has received an injection of a vaccine that will keep them safe from the zombies virus.