The film is set in Colorado during the year 2035, a time when a catastrophic viral outbreak has decimated a significant portion of the Earth's population. The story follows a young man named Hig, played by Jacob Elordi, who navigates his post-apocalyptic surroundings alongside his loyal dog, Jasper. Hig often journeys back to his former home in Denver, where he once shared a life with his pregnant wife, Melissa, portrayed by Sai Bennett.
As he ventures out, Hig encounters a scavenger played by Ewen Bremner, who uses a crossbow to threaten him. Although Hig manages to frighten the scavenger away with his rifle, a warning is issued about a violent group of hunters known as the "Reapers," who are notorious for their savagery. Nonetheless, Hig continues his mission and flies supplies to a secluded Mennonite community led by Aaron, played by Benedict Wong. This community, isolated from the remnants of civilization, has been affected by the virus but is well-supplied and possesses electrical power.
After returning to his home base, an abandoned airfield shared with Bangley, played by Josh Brolin, Hig expresses a desire to seek a better life by flying out to Grand Junction. Bangley, a former marine, is cautious about Hig's plan but ultimately offers him his support. They soon discover two young scavengers lurking in the distance. Bangley acts swiftly by sniping them, but Hig soon realizes their guns were unloaded, leading to Bangley burning the bodies to eliminate any trace of danger.
As night falls, a new group of scavengers encroaches upon their territory, resulting in a tragic confrontation that leaves Jasper fatally wounded. Stricken with grief, Hig buries his beloved companion next to Melissa's grave. Despite Bangley’s advice against it, Hig resolves to head to Grand Junction. After bidding farewell, he sets out only to encounter mechanical failure mid-flight, necessitating an emergency landing in a nearby meadow.
During his unexpected stop, Hig is almost trampled by a herd of buffalo, leading him to the home of a young woman named Cima, played by Margaret Qualley, and her father, Pops, portrayed by Guy Pearce. Pops initially confronts Hig with hostility, ordering him to disarm. However, as Hig explains his situation, a tentative understanding begins to form.
While Hig works on repairing his plane and clearing space for a runway, Cima takes it upon herself to help him by bringing food. Their shared experiences lead to a developing bond, prompting Pops to ultimately assist Hig in his efforts. However, their newfound peace is soon disrupted when a marauding group of raiders attacks their farm. In a fierce battle, they manage to fend off these intruders, with exciting moments that include a daring takeoff as one raider is severely injured in the process.
Meanwhile, back in Erie, Bangley faces a large horde of Reapers descending upon the area. In a desperate bid for survival, he fights valiantly against the odds, retreating to a tower where he picks off enemies, only to find himself outmatched when a rocket attack brings the structure crashing down.
Upon finally arriving at the Grand Junction Regional Airport, Hig, Cima, and Pops encounter a camp of survivors led by the formidable Darlene, played by Allison Janney. At first glance, the group appears friendly, but a sinister undertone quickly resurfaces as Darlene attempts to coerce Cima into an unwanted marriage to one of her soldiers. In a critical moment, Hig creates a diversion by starting a fire, allowing Pops to eliminate some of Darlene's guards, enabling their escape. The trio races against time as they uncover a grim reality of cannibalism amid the dead bodies scattered throughout the airport.
In an intense climax, they manage to fight their way back to the aircraft, where Hig communicates with Darlene through a radio, rejecting her despairing thoughts about their bleak future. In a dramatic turn of events, he orchestrates an explosive farewell, dropping grenades upon the throngs of survivors, ensuring their escape by obliterating the threat behind them.
Returning to Erie, Hig's relief is palpable as he reunites with Bangley, who has survived the ordeal, albeit wounded. They gather whatever supplies they can find and make their way back to the Mennonite community. In a tender moment, Cima interacts with the children of the community, and later the group comes together for a musical celebration, showcasing hope amidst chaos.
As night falls once again, Hig and Cima venture out into the serene field, gazing up at the stars. Hig shares a poignant moment with her, revealing that he has named a constellation after Jasper, aptly dubbed "the dog stars.” Underneath the vast sky, their affection for one another blossoms as they share a gentle kiss, signifying a flicker of hope in a world overcome by despair.
