The US Government launches a devastating chemical weapons attack on its own citizens, intending to create a societal "reset." As a result, the surviving population splits into two distinct factions: the Gangs, who exert control over specific territories and adopt unique themes—such as The Gamblers, Sheets, Plowboys, Nailers, and Cherries—and the Domestics, composed of those who remain unaffiliated and seek a peaceful existence away from the gangs' brutality.
Amid this chaos, a couple, Mark and Nina West, are en route to Milwaukee to visit Nina's parents, grappling with their impending divorce prior to the catastrophe. During their journey, they encounter fellow survivors, Nathan Wood and his son Steven. This chance meeting occurs while they scavenge for essentials and narrowly escape a small group of Nailers. Invited to Nathan’s home for a meal along with his wife and daughter, the visit soon turns tragic when Nathan discloses that the meal they shared included human flesh. Their gathering is abruptly broken apart by a retracing Nailer who injures Nina, forcing the couple to retreat and leaving the Woods to face a grim fate at the hands of the attacker. Nathan, fueled by vengeance after killing the Nailer, reaches out to his Plowboy connections over the CB Radio to seek retribution against the Wests.
Seeking refuge in an abandoned house, Mark and Nina inadvertently attract the attention of a deserter Cherry named Betsy. Having recently escaped from the Plowboys' captivity, Betsy becomes infatuated with Nina. While Mark scavenges for supplies, he finds himself caught off guard and held hostage by William Cunningham, a flamboyant and deranged man. Mark is coerced into fighting a massive slave under William's command after discovering that Nathan and Steven have pursued them, only to be captured by Cunningham as well. Meanwhile, Nina awakens to a bottle of alcohol, plays a heavy metal record left by Mark, and begins to dance, oblivious to the ongoing danger. In a fierce confrontation, Mark defeats the slave and ultimately kills William. The freed slave, feeling sympathy for Mark’s plight, departs alongside Nathan and Steven, leaving behind a heartwarming message of forgiveness and well-wishes.
Reunited, Mark and Nina explore the house and stumble across an old car reminiscent of one Mark owned when they first fell in love. Their connection rekindles, yet they fail to note the vehicle’s connection to the Gamblers. This oversight leads to their capture, and they find themselves participating in a deadly game of Russian Roulette, resulting in Mark sustaining a shoulder wound. Taking advantage of a moment of distraction, Nina manages to seize a gun and escape, ultimately arriving at her parents' house, where she tends to Mark's injuries.
Devastated to learn from neighbors about her parents' deaths, Nina’s shocking revelation is exacerbated when Mark discovers that his father-in-law's prized Wildey Hunter Pistol has been stolen. The tension escalates as the Gamblers and Betsy track them down, igniting a brutal gunfight that also sees the Plowmen joining in. In a gripping climax, Mark and Nina emerge victorious, forcing the Gangs to retreat. As the chaos subsides, Betsy returns Nina's wedding ring to Mark, uttering “for her” before being fatally shot, prompting Nina to avenge her by killing Betsy’s assailant. Nina locates her father’s gun at a neighbor's home only to uncover the dark truth about another neighbor's child, who is rumored to be part of a gang of youthful killers, as alluded to by Nathan.
Taking a moment to breathe amidst the turmoil at Nina’s family home, Mark and Nina share a tender embrace before packing up to leave. They switch on the radio to listen to Crazy Al, a DJ broadcasting updates about the ongoing chaos in America, who sends a warning to the Gangs: mark and Nina are not to be trifled with.
