A disgruntled employee steals 12 vials of a genetically modified virus. In his haste to escape, the thief gets into a fatal car accident. One of the twelve vials gets hurled into a fast flowing creek and floats downstream into a lake. A mother and daughters, along with their dog are vacationing in a near by cottage. On their morning walk the dog finds the hazardous vial and consumes the virus. Next morning the dog reacts aggressively toward the mother, eventually attacking and tearing at her ankle, in short, infecting her. When the dog attempts to attack the little girl, the mother manages to violently force the animal out of the cottage and into forest where government agents come across the animal and shoot it.
Back at the cottage and realizing that she is infected and might harm her own child, the mother chains herself to a steel beam and orders her daughter that under no circumstance is she to be released. Eventually the mother succumbs to the virus's potency and develops the urge to infect her own daughter. She begs to be released but the child refuses leaving the enraged mother to savagely chew off her own wrist in order to get at her daughter. The child escapes and eventually is recued by government soldiers. The soldiers in turn capture the mother and she is taken to a lab where can be analyzed.
Doctors discover that the child is now also infected and plan to put her to death but once the mother finds out, she escapes and begins a violent search for her daughter