As two truckers transport hazardous materials, a careless error leads to the release of a toxic canister that dramatically disrupts the tranquil existence of a beaver community by a serene river. This cylindrical container floats downstream, shattering the peaceful atmosphere as it breaches the beavers' carefully constructed dam, forcing them into a frantic race to rebuild their home.
Meanwhile, college friends Mary (no actor provided), Zoe, and Jenn arrive at Mary's cousin's secluded cabin located near the dam. Initially disheartened by the lack of cell phone reception, Mary insists on unplugging from technology and drama for the next two days. Enjoying a leisurely swim in the lake, they stumble upon the beaver dam, and Jenn, driven by curiosity, approaches closer, only to be startled by an unexpected bear encounter.
Enter Smyth (no actor provided), a local hunter who skillfully drives the bear away and warns the girls to steer clear of the beavers while dressing more appropriately for their surroundings.
As the night descends, Mary's boyfriends - Buck, Tommy, and Sam (no actors provided) - arrive with mischievous intent to prank the girls. Mary swiftly orders them to leave; however, Zoe, who knows of their impending arrival, argues in favor of them staying. Jenn's relationship tensions with Sam, who has betrayed her, make her rethink her earlier stance. This results in a temporary cooling of tensions, allowing the couples time apart to pursue their individual interests.
Yet, Jenn’s solo shower takes a terrifying turn as she is suddenly attacked by a beaver. Tommy quickly responds, defending her with a baseball bat, but Jenn remains troubled by the creature's odd behavior. When they dispose of the defeated beaver on the porch, it mysteriously disappears, further deepening Jenn's suspicions of something lurking behind the facade of their idyllic getaway.
As discord begins to lace through their group, Sam and Mary whisper about their secret affair, only to find themselves interrupted by a wave of disturbing events. The beavers, now driven by an inexplicable aggression, inflict gruesome injuries on Buck and Tommy, while the same sinister force that attacked Jenn earlier relentlessly pursues her back to the cabin.
In a bold move, as Zoe’s dog is thrown into the water to misdirect the beavers, the rest of the group flees to their cabin, only to discover that their phone lines have been severed, isolating them completely. With the beavers closing in like vengeful zombies, Tommy suggests they abandon the cabin to seek help, taking Buck and Zoe with him. However, their journey is abruptly halted when a massive tree crashes down, tragically killing Tommy.
After Smyth intervenes to help Buck and Zoe, their nightmarish adventure continues as they attempt to navigate the devastated landscape. The trio arrives at a neighbor's house, only to stumble upon the horrifying remains of what seems to be a violent attack, with phone lines laying on the ground like severed limbs. Amid this chaos, Jenn's wounds begin a grotesque transformation, turning her into a beaver-like creature, fiercely attacking Mary with wild abandon.
In a fierce confrontation, Sam heroically steps in, delivering a crushing blow to the transformed Jenn. As Mary and Sam fortify themselves within the cabin, they momentarily lose track of their horrific reality, sharing a brief moment of passion, only to be brutally interrupted by Jenn's feral assault, resulting in catastrophic consequences for Sam.
Simultaneously, Buck undergoes his horrifying metamorphosis into a ravenous beast, launching an attack on Smyth. Zoe narrowly escapes the horror by leaping through a broken window, emerging battered yet determined. When Mary and Zoe find each other amidst the chaos, they are met with a shocking new threat—Smyth, now a mindless creature, takes aim at them with a hail of bullets from his truck.
In a moment of high tension, Jenn scales the out-of-control vehicle, but Zoe acts swiftly, delivering a decisive strike that sends Jenn tumbling to the asphalt while they grapple with their fears. As they reach the tragic site of Tommy's demise, they are forced to abandon the truck, striking out on foot amid the uncertainty that lies ahead.
As they traverse this perilous terrain, an unsettling suspicion gnaws at Mary—could Zoe have been bitten? Hovering on the precipice of dread, Mary's weapon is drawn, a grim decision hanging in the air. In a shocking twist, Marie's transformation into a mindless zombie accelerates, compelling Zoe to take drastic measures to put an end to her friend’s suffering.
As she departs from the horrific scene, fate takes a cruel turn when the same truckers, who began this chain of turmoil, accidentally run Zoe down. In a chilling post-credits scene, a honeybee finds its way back to its hive, only to emerge transformed into a zombified creature, ready to spread its horrifying influence across this devastated world.
