Jake Stephens is a well-known slacker at Ronald Reagan High School. He has no talents besides his skill at video games and has no ambitions in life, except to possibly gain the attention of Amanda Blake, his secret crush. On an otherwise normal day, he goes to school and notices that his stomach is growling abnormally loud. At lunch, he feels hungry and dizzy and his vision goes pink, then red. Then he hears screams from across the room and sees Amanda Blake devouring her best friend. Rather than be disgusted by the scene, Jake stands up and attacks his best friend, too.
Cass is a teenage telepath working for the Necrotic Control Division of the government. She arrives at Ronald Reagan High School (RRHS) after Jake and Amanda kill and eat about 30 of their classmates. She touches objects belonging to the recently deceased to get mental pictures of the incident.
Cass is shocked to discover that there were two zombies involved in the carnage this time. She establishes a loose psychic link with Jake, and she is tasked with finding him and Amanda, who have fled the scene. Normally, zombie minds are cold and empty, filled only with the instinct to feed, but Cass notices that Jake is still thinking exactly like other humans.
After they recover their senses, Jake and Amanda find themselves in a parking lot near their school. They remember the incident only vaguely and realize they must run away if they want to avoid being arrested for their crimes. Amanda hotwires a car, and Jake drives it.
Cass rides in a military vehicle with Jamison, her team’s combat specialist, and Tom, her best friend and keeper. After a brief car chase, Jamison decides to ram Jake and Amanda’s car, against orders from Harlene, the head of the NCD, and stops them
When Jake emerges from his vehicle, Jamison shoots him in the stomach. Amanda picks up Jamison and throws him across the street. Jake and Amanda run away and find shelter in a funeral home. They eat the morticians who work there and discover that human flesh makes them heal from severe wounds, and they can regrow body parts.
At RRHS, Harlene tells traumatized students that they witnessed a school shooting, not a zombie attack. Cass telepathically nudges the students’ brains to receive the information as the truth. Amanda’s boyfriend Chazz is an also infected with the zombie virus and bites a chunk out of Harlene’s arm. To keep Chazz from killing Harlene, Cass reaches out with her mind and knocks him unconscious, something she shouldn’t be able to do. Harlene’s superior, a powerful yet creepy telepath named Alastaire, notices Cass’ new skill with interest.
At the funeral home, Jake and Amanda change clothes and rest for the night. In the morning, they see themselves on the news but notice that the details of their story are lies. The news completely hides the outbreak of the zombie virus and says the two were school shooters, but are now in police custody. They realize they need to leave the state, so they pack some clothes and steal the morticians’ station wagon. Amanda wants to drive to Michigan to see her brother Kyle, who enjoys conspiracy theories, especially zombie-coverup conspiracy theories. She thinks Kyle may have information that could help them.
On the radio, they hear that Amanda’s ex-boyfriend Chazz has murdered his parents and grandparents. Amanda realizes his story is a coverup also and that Chazz almost must be a zombie, too. She guesses that since the zombie virus isn’t spread by biting people, it might be transmitted sexually. Her theory is confirmed when Jake says that his zombie symptoms began after he had unprotected sex with a college girl he met at a bar. As their car drives through Pennsylvania, Jake gets hungry. His skin turns ashy gray, and his heart stops. He begins to attack a gas station attendant, but Amanda and two female zombies stop him.
Cass is exhausted after knocking out Chazz, by just using her mind. Even though she’s tired, Alastaire wants to test the range of her abilities. He tries to get Cass to forcibly alter the memories of RRHS’s assistant principal Hardwick, a woman who has a stronger mind than most and who refuses to stop referring to the incident as a zombie attack.
Cass doesn’t want to warp Hardwick’s personality by forcing her mind to accept false information, and Alastaire is disappointed in Cass’ weakness. Alastaire is also disappointed that Cass feels sympathy toward Jake, even though he’s a fugitive zombie. Cass decides not to tell Alastaire that she still has a clear mental connection with Jake and could help the NCD find him and Amanda. She has a bit of a crush on Jake.
Jake wakes up in a basement with Amanda, both of them having been captured at the gas station by a lesbian zombie couple named Grace and Summer. Grace and Summer stopped Jake from rampaging and killing the gas station attendant the previous night. They fed him a raccoon and brought him and Amanda back to their house. When Jake and Amanda decide to continue their road trip, Grace and Summer give them a carrier full of rats to eat, plus a roadmap marking the locations of morally questionable people they could kill and eat on their way to Michigan.
Cass attends a Prayer and Remembrance event at a megachurch in Jake and Amanda’s town to see if the NCD’s official story has solidified in the minds of the attendees. Outside, Cass sees Jake’s little sister, Kelly, and is horrified when Alastaire arrives and psychically pushes Kelly until she enters his car.
Alastaire takes Kelly to a testing facility where he has been working on controlling zombies, getting them to follow his commands. Alastaire connects himself to Chazz via a tube that runs from Alastaire’s wrist to Chazz’s skull. The tube feeds some of Alastaire’s blood to Chazz when Chazz does what Alastaire wants. Alastaire threatens to let Chazz eat Kelly unless Cass tells him where Jake is.
Instead of divulging Jake’s current location, Cass sends the NCD to Grace and Summer’s hideout. Jamison shoots Summer, killing her. The NCD traps Grace in a net, planning to contain her as an asset.
Jake and Amanda eat a creepy trucker in a gas station bathroom, and then kiss for the first time. They continue traveling and arrive at Kyle’s house in Michigan, but can’t visit because the place is under government surveillance. They disguise themselves and contact Kyle through a conspiracy theory message board to ask him to meet in a public place.
On the message board, they hear that someone in Iowa has found a zombie cure. Jake and Amanda meet Kyle and tell him about the government cover-up of the zombie crisis. NCD agents arrive and shoot at them. Amanda attacks and eats one of the government agents. Then she and Jake steal a new car and begin driving toward Iowa, determined to find the cure.
Sensing Cass’ growing discontent with her situation, Harlene offers Cass a chance to leave the NCD. If Cass helps them find Jake and Amanda, she can stop being a telepathic agent and go home to live a normal life. Cass signs the paperwork and leads her team to a farmhouse near Iowa where Jake and Amanda have stopped. Alastaire sends Chazz to fetch them. Chazz attacks, but Jake is able to fight him off. Other members of the NCD attack Jake and Amanda. Amanda bites a chunk out of Harlene’s neck, killing her.
The NCD captures Amanda, but Jake runs away from the farmhouse and into a wheat field. There, he encounters a zombie gang who save him from being caught by the NCD. The zombie gang captures Jamison and a few other NCD agents, telling Jake that they are tribute for their leader. The zombie gang decides to go back to the farmhouse to eat the remaining NCD agents, and Jake goes along to try to rescue Amanda.
At the farmhouse, Cass manipulates Chazz’ mind so he will attack Alastaire. Chazz bites Alastaire’s arm, and then Cass’ friend Tom shoots Chazz in the head, killing him. The zombie gang descends on the farmhouse and begins eating the agents. Terrified, Cass runs away from the farmhouse. When she sees Jake outside amid all the carnage, she hugs him like a long-lost friend, although Jake has no idea who she is, since their psychic connection was a one-way link. Cass offers to help Jake find the man with the zombie cure. Cass and Jake free Amanda, and Jake tells Amanda he loves her. Cass, Jake and Amanda drive to the outer border of Iowa, then stop, unsure of their next move.