In the oppressive heat of summer 1981 on the Red Crow Indian Reservation in Quebec, Canada, Gisigu makes a startling discovery during his daily fishing routine: the gutted salmon refuse to stop twitching. Meanwhile, Sheriff Traylor is called to address a troubling situation involving a dying dog, owned by his estranged wife, Nurse Joss. With a heavy heart, Traylor is forced to administer a mercy shot to the suffering creature. His visit to Joss unveils a grim reality— their son, Joseph, has been arrested for vandalism in Hollarbaster and is locked up with his half-brother, Lysol. Upon returning to his home, Traylor is greeted by the ominous sight of the still-writhing fish. The deceased dog reanimates in the trunk of his police cruiser, pushing Traylor to once again resort to brutal measures to free it from suffering. Together, he and Gisigu consign the dog and the tortured fish to flames.
As darkness envelops the land, Traylor, alongside Joss, embarks on a daring mission to rescue Joseph from jail. They are joined by Lysol and Police Officer Shamu, but their journey quickly descends into chaos when they encounter a rabid individual who viciously bites Joseph. Rushed to the hospital, Joseph faces the worried gaze of his white, expectant girlfriend, Charlie. That same night, a call from local resident Shooker leads Traylor into an ambush by Shooker's white companion. Armed and ready, Traylor takes out the assailant before teaming up with Shooker to reach a bridge where Joss, Joseph, and Charlie are hiding after a brazen escape from an ambulance.
Fast forward six months— the ominous "zed" plague has ravaged the region, forcing the inhabitants of the Red Crow Reservation into a fortified safe haven. The indigenous community discovers an unusual immunity to the flesh-eating disease, while the white population is devastated. Tensions rise within the compound as Lysol grows increasingly frustrated with Joseph’s habit of bringing outsiders— including a man and his young daughter with visible bite wounds, as well as Lilith, who shields her own infection—into their midst.
As night falls over Lysol’s makeshift sanctuary, Joseph stumbles upon a horrific scene: Lilith, a former community member, has turned into a savage zombie, feasting on Lysol's mutilated flesh. The urgency of the situation escalates as they flee back to the compound, struggling to contain the fraught Lilith. Fueled by pain and desperation, Lysol finds himself blaming the growing presence of white survivors for his injuries, culminating in an explosive confrontation with Joseph. In a moment of rage, Lysol unleashes Lilith within the compound, setting off chaos among their previously safe community.
Meanwhile, Traylor and Gisigu return from a mission to eliminate zombies at a nearby gas station, only to discover their home has been overrun by the very creatures they sought to eradicate. They learn that Joseph, Joss, Charlie, and eight other survivors are trapped in the basement, desperately needing rescue. As Gisigu and Bumper attempt to free them, Traylor heroically sacrifices himself to the ravenous horde, ensuring his family can escape.
The remaining survivors— Joss, Joseph, and Charlie— manage to flee with Gisigu and Bumper. As they navigate their perilous surroundings, Joseph and Gisigu enter a church to confront two of Lysol’s associates who wish to slaughter a group of survivors. Unbeknownst to them, Lysol lies in ambush and brutally attacks Bumper, gravely wounding him. In response, Joss retaliates and strikes down Lysol, who, in his dying moments, releases a zombie from the trunk of a nearby vehicle.
As the chaos unfolds, Charlie finds herself bitten and infected, clinging to life as the group barely escapes the onslaught of zombies. In a moment of grim desperation, Joseph delivers a critical blow to Lysol, ensuring the safety of his friends. As Gisigu aims a shot into the air to distract the undead, it tragically draws the horde towards Lysol, sealing his fate.
With their options dwindling and hope waning, the group discovers a lone boat on the shore, engulfed in flames. Shooker returns heroically with two vessels, whisking Bumper to safety while Joseph, Charlie, and Joss set sail into the unknown on their own craft. Armed with only a sword, Gisigu remains behind to battle the undead, appearing victorious— for now.
As they drift further from land, Charlie goes into labor, her life slipping away from the bite that threatens to transform her into one of the monsters they fear. Overwhelmed by grief, Joseph ends Charlie's suffering, his tears commingling with the sea spray. And so, with their fates uncertain, they are lost at sea in a world unraveling before their eyes.
