Teenager Curt Reynolds steals his father's security key card, embarking on an adventure with his girlfriend, Julie. Their exploration leads them to the military base where Curt's father, Colonel John Reynolds alongside Col. Peck and Lt. Col. Sinclair, supervises a shocking experiment involving a deceased body exposed to 2-4-5 Trioxin gas, resulting in its reanimation as a zombie. The military envisions using these creatures as combat units, but quickly discovers their uncontrollable nature, driven by an insatiable hunger for human brains.
In an attempt to manage the zombies, Sinclair proposes a method to attach them permanently to exoskeletons, while Reynolds advocates for a chemical approach called "paretic infusion." This method aims to freeze the zombie's brain temporarily. However, during a lab test, the infusion proves insufficient, allowing the zombie to attack and kill a scientist. As the chaos unfolds, the bites lead to a chain of reanimations, resulting in quarantined survivors and Reynolds’ reassignment to Oklahoma City, whereas Sinclair takes control of the project.
Faced with another relocation, Curt and Julie flee, but tragedy strikes when a playful moment distracts Curt while riding his motorcycle. Julie is thrown against a telephone pole, dying instantly. Devastated, Curt brings her body back to the military base and uses his key card to access the Trioxin gas, desperate to bring her back to life. After a temporary reanimation, Julie and Curt confront the ghastly reality of her new state—free from pain but also devoid of a normal appetite.
As hunger strikes, the couple ventures to a store where an altercation with a gang erupts. In the ensuing chaos, Julie's primal urges emerge, leading her to consume a fresh corpse. They escape only to find themselves hiding in the sewers with Riverman, a vagrant who provides refuge. Here, Julie discovers pain as a means to suppress her cravings, leading to a brutal self-mutilation that adorns her body with spikes and glass.
When the gang discovers their hideout, Julie seduces their leader before gruesomely dispatching him with her new weapons. As her body grows more acclimated to the pain, she turns on Riverman, killing him and leaving a trail of chaos behind. Meanwhile, the military closes in on the zombies, knowingly or unknowingly capturing and neutralizing them after the gang is dealt with.
Realizing that Julie's fate is sealed as a military asset, Curt succumbs to rage, releasing the zombies in a bid to save her. The ensuing mayhem leads to a fiery conclusion at the base, where Curt is bitten by the very zombie from the beginning. In a heartbreaking moment, Curt's father pleads with him to escape, but Curt’s loyalty remains with Julie. In their final act, he leads her to the furnace, uttering, > “where we belong,” as their lips meet one last time, surrounded by flames and fading to darkness.
