In a remote woods, a hermit named Henry confronts a grim moment when his dog dies from a mysterious illness and, in a shocking turn, blood from the dog sprays onto Henry himself. Nearby, five friends—Paul, Karen, Bert, Jeff, and Marcy—have rented a secluded cabin for a week-long vacation, hoping to escape the noise of everyday life and soak in the quiet of nature.
Their trip begins with a stumble into danger at a General Store where Dennis, the manager’s mentally impaired son, unexpectedly bites Paul, hinting at something lurking beneath the surface of their carefree retreat. The woods soon become a stage for misfortune: Bert ventures off to shoot squirrels and inadvertently shoots Henry, whose illness becomes the centerpiece of fear and panic. Realizing Henry is infected, Bert flees, determined to keep the secret of what he’s seen.
That night, a mysterious intruder named Grim arrives with a Belgian Malinois named Dr. Mambo, interrupting the group’s campfire ritual and injecting an unsettling tension into the cabin’s already fragile sense of safety. Not long after, Henry himself stumbles into the cabin, seeking help, only to be rebuffed when Bert doors him out. In a desperate struggle, Henry tries to steal a vehicle, and the confrontation escalates into a dangerous inferno that leaves the car crippled and the desperate man fleeing into the woods.
With the dawn comes a new search for help. Jeff and Bert head out, hoping to find someone who can explain what’s happening. A farmer offers assistance, but the moment they learn Henry is her cousin, she withdraws, terrified of the implications. Meanwhile, Deputy Winston arrives to investigate the previous night’s disturbances, and Paul speaks in broad terms about the chaos, avoiding mention of Henry’s fate. Winston promises to arrange a tow, then moves on.
Dr. Mambo reappears at the cabin, appearing infected and menacing, though the dog-wielding threat is thwarted when Marcy uses the rifle to scare him off. As Paul and Karen share a moment of intimacy, they uncover a startling fact: Karen is infected with the flesh-eating virus and her leg is beginning to decay. The group’s fear of contagion leads them to lock Karen in a shed, while Paul sets off on foot to search for help, only to be pushed away by strangers who mistake him for a peeping Tom.
The next morning’s failed evacuation becomes a nightmare. Karen vomits blood, staining the car’s interior and signaling the spread of the disease. Bert drives to the general store alone, while Jeff abandons everyone and flees to a remote shack. Marcy and Paul, hanging onto a fragile hope of survival, share a moment of closeness, only to confront the grim reality that they, too, are likely to succumb. They later discover marks on Marcy’s back, a cruel sign that she is also sick.
At the general store, the virus claims another victim: Dennis bites Bert’s hand just as he did Paul. Tommy, Dennis’s father, lashes out in anger over the exposure, and the two confront the group, forcing Bert to run for safety. In a harrowing encounter, Paul stumbles upon Henry, badly burned yet alive, in the lake. Henry attacks Paul, who fights back and ultimately kills him, ending one terrifying chapter of the nightmare.
Marcy’s distress escalates as she prepares a bath and shaves her legs, only to have the infected flesh peel away in gruesome strips. She staggers outside and is mauled to death by Dr. Mambo, the dog that has become a catalyst of horror. Paul returns to the boat shed to find Karen begging him to end her life; with the gun empty and unable to strike, he makes a desperate choice and sets the shed ablaze, watching in horror as Karen herself is burned alive.
Back at the cabin, Bert makes it home only to be shot dead by Tommy, a brutal reminder of how quickly friends become enemies in this nightmare. Paul seizes Bert’s rifle and turns his anger toward Tommy and his two accomplices, ending their threat with deadly precision. He escapes in Tommy’s truck, but a crash into a tree and subsequent explosion obliterate the vehicle, leaving Paul bloodied and momentarily adrift. A hazmat crew and authorities arrive, and Deputy Winston receives a radio directive to shoot Paul on sight. Yet Paul manages to persuade her to let him go, buying him a temporary escape from a fate that seems all but certain.
The following morning, Jeff returns to the cabin, only to discover the still and silent aftermath: the bodies of his friends and Tommy’s accomplices. He exults in presumed survival, only to glimpse the infection’s signs on his own hand and be shot dead by Deputy Winston with a sniper rifle. Paul, overwhelmed by the infection, collapses in the woods as Dennis finally discovers his corpse. In the cabin’s wake, officials and a hazmat crew sweep the scene clean, with a final, grim reveal: Jeff’s corpse lands near a lake whose water now bears the taint of his contagion, hinting at an ominous spread that may linger long after the escape attempts have failed.
This chronicle of fear and survival blends sudden violence, escalating paranoia, and the inexorable reach of a mysterious illness, leaving an uneasy impression of how quickly a group’s simple vacation can devolve into a relentless battle against an unseen, unstoppable threat.
