In the quirky town of Dillford, Ohio, a fragile equilibrium exists among three peculiar groups: humans, vampires, and zombies. The vampires, basking in their undeniable superiority, occupy the highest social ranks, while the zombies are relegated to their own segregated quarters, restrained by special collars that enforce their compliance. Humans find themselves in a tense middle ground, overshadowed by the vampires' arrogance and regarding the zombies as mere second-class citizens.
Amid this societal tension, Dag—a self-identified school nerd—embarks on a mission to lose his virginity to Lorelei, the most coveted girl at school. This endeavor is driven by his desire to prove himself and shed the label of being a failure. However, his plans are persistently sabotaged by Rick Wilson, a grumpy baseball coach and meat factory manager. Rick has unjustly fired all the human workers, including Dag's mother, opting to replace them with far cheaper zombie labor. The emotional scars from this injustice simmer just below the surface, threatening to erupt.
Dag's frustration reaches a boiling point during a practice when he finds himself taunted by Rick. In a moment of pressure, he chokes on his pitches and inadvertently injures a star athlete. Following this incident, his hippie parents attempt to console him, but their well-intentioned advice only deepens his embarrassment.
Meanwhile, Petra, a social misfit, undergoes a dramatic transformation into a vampire after a passionate encounter with Milan, the charming playboy of the school. However, when Petra seeks to escalate their relationship, Milan’s cruel rejection leaves her isolated and struggling to adapt to her new undead existence.
As Dag battles his personal demons, he also confronts the consequences of past decisions. His former best friend Ned, ostracized by his own family due to his intellectual pursuits and lack of athletic skill, resorts to desperate measures to escape high school pressures. After a heated argument at home, he ventures into the zombie ghetto and chooses to embrace the undead life by allowing himself to be bitten by a female teenage zombie.
Just as Dag is on the verge of sealing his deal with Lorelei, the peace in Dillford shatters with an unexpected extraterrestrial invasion. This chaos ignites a catastrophic conflict between vampires, humans, and zombies, creating havoc throughout the town. Seeking refuge, Dag and Lorelei find themselves trapped in a house that quickly succumbs to a horde of ravenous vampires, leading to Lorelei appearing lifeless due to the actions of Petra—whose jealousy has bubbled to the surface.
As the chaos intensifies, Dag, Ned, and Petra are forced to flee their homes and seek sanctuary in Stuart Miller's underground lair, which serves as a hideaway presided over by the town's resident doomsday prophet. In this dark and claustrophobic setting, Petra and Ned are driven by their overwhelming hunger, leading to a gruesome spectacle as they contemplate devouring Stuart and his mother.
The invading alien forces, now aware of Dag and his group’s location, launch an assault on their high school. This leads to rising tensions between Dag and Ned, culminating in a severe rift in their friendship. Driven by his zombie nature, Ned seizes the chance to abandon Dag and go it alone. During a moment of confinement, Dag and Petra share an intimate connection, though Dag's fear becomes evident, further aggravating Petra's insecurities.
Unrelenting, the extraterrestrial threat closes in on Dag and his companions, who scramble to devise a plan for evasion. They uncover the aliens' peculiar weakness: an inability to detect organic materials. Armed with salvaged natural fibers from Dag's mother, they brave the confrontation with their otherworldly adversaries.
In a shocking twist, Dag, Petra, and Ned are captured by the aliens and imprisoned with other Dillford captives. The force fields that separate the humans, vampires, and zombies serve as a stark reminder of the aliens’ overwhelming power. In the midst of despair, Lorelei—thought dead—is revealed to have been transformed into an exceptionally enchanting vampire, sending shockwaves through Petra's previously unwavering confidence. Faced with the opportunity to unite against their alien captors, Dag, Ned, and Petra rally their fellow prisoners to devise a strategy that transcends their differences and reclaim their town.
At Rick Wilson's meat processing plant, the secretive substance Tetrafluoraxipan holds the key to an otherworldly revelation. The aliens, enticed by this mysterious compound, swarm the factory as Dag persuades Rick to allow the townspeople entry. As the aliens soak in the chemical, they merge into a colossal being, which mistakenly assumes they come in peace. The furious townsfolk disrupt its condescending speech, triggering a chaotic fight. Realizing the ammonia tanks in the factory can incapacitate the alien, Dag seizes the moment.
With a turn of events, Milan’s nefarious plot to eliminate Petra is thwarted by Dag, who unexpectedly transforms into a werewolf after dodging death. His new form proves crucial during the ensuing melee, resulting in Milan’s accidental demise when he becomes impaled on a metal pole.
As the solitary alien reverts to its diminutive size and attempts to escape, it unwittingly drops a bomb destined to destroy the town. In an act of courage, Ned catches the explosive, proving himself capable despite being a zombie. He passes it to Dag, who expertly pitches the bomb into the alien ship just as it seals its doors, resulting in a massive explosion that obliterates the extraterrestrial threat.
In the aftermath, as normalcy returns to Dillford, Lorelei approaches Dag with a romantic overture, only for him to reject her in favor of Petra. Meanwhile, Ned appears content with his undead existence, forming an unlikely bond with his star athlete brother, each having navigated their own unique transformations.
