Alex, portrayed by Jack Gore, is a socially withdrawn teenager grappling with the recent loss of his father in a tragic fire. Reluctantly, he finds himself at a summer camp in Southern California called Rim of the World. There, he connects with two other outcasts: Zhen Zhen, an initially silent but charming orphan from China, played by Miya Cech, who managed to bribe her way into America for this experience, and Dariush, an outspoken boy from a wealthy family, played by Benjamin Flores Jr.. The group's unofficial leader, Logan, is represented by Andrew Bachelor. Despite the summer atmosphere, Alex is held back by his debilitating fear of heights, which prevents him from participating in the zip line activity.
One afternoon, while enjoying some leisure time by the lake, Zhen Zhen ventures off into the woods, inspired by a lookout point she spotted in a camp poster. Alex, eager to follow, encounters Dariush, who is away from the group. In a comically misguided attempt to help Alex overcome his fear, Dariush insists he stand near a cliff. Their conversation is interrupted by Gabriel, a mysterious new boy in camp, played by Alessio Scalzotto. Witnessing the chaos brings Zhen Zhen back, and just then, their phones buzz with urgent messages demanding immediate evacuation.
The friends are soon alarmed to see explosive bursts illuminating the sky, later identified as EMPs responsible for knocking out electronic devices worldwide. Rushing back to camp, they discover the alarming sight of alien ships invading the valley amidst a frantic atmosphere. Upon reaching the camp, they find it eerily deserted aside from Conrad, the camp counselor. Meanwhile, a damaged dragon spacecraft crashes nearby, from which a dying astronaut hands Alex a crucial key, instructing him to deliver it to NASA's Jet Propulsion Laboratory (JPL) in Pasadena, as it’s the only means to combat the aliens. Tragically, the astronaut is killed by an alien creature shortly after, prompting Alex and his friends to find refuge as they evade this dangerous enemy.
Even though JPL is 70 miles away, Zhen Zhen suggests they can simply hand the key to a government official instead. Their journey leads them to a sheriff's office, where they encounter a prisoner named Lou, portrayed by Scott MacArthur, who claims to have a son waiting for him. Moved by Lou's plea, Alex decides to help him escape. Later, they cross paths with Marines who are evacuating civilians; the commander gratefully accepts the key, but when alien ships attack, the chaos results in the soldiers’ deaths, and Alex retrieves the crucial key from one of the fallen commanders.
As night falls, they take shelter in Gabriel’s former home, where he reveals his troubled past as a juvenile escapee due to a misunderstanding involving Dyscalculia. However, danger strikes again as they are ambushed by a gang led by the treacherous Lou, who shows his true colors as a criminal. Lou attempts to coerce Alex into surrendering the key, but refuses and a fight ensues. Just then, a pursuing alien appears, attacking Lou and his allies. In the chaos, the kids manage to thwart the alien, trapping it in a swimming pool.
As the group continues through the forest, tension mounts when Dariush confesses his family's lost dealership has forced him to camp. Suddenly, they receive a desperate S.O.S. call from JPL, encouraging them to persist in their mission. The children change into more practical clothing at a mall and commandeer a Ford Mustang, discovering Zhen Zhen's hidden talent for driving. However, as they speed toward their goal, they encounter the alien once more. In the scuffle, Dariush bravely retrieves the key from the abandoned vehicle, despite sustaining injuries.
Arriving at the JPL facility, they find the key's recipient dead—a grim revelation of the chaos they have faced. Nonetheless, they manage to establish communication with a general at NORAD, who explains the key is vital in activating an old Cold War defense project named Excalibur, necessary to obliterate the alien mothership hovering above. Zhen Zhen descends into the basement to initiate emergency power while Alex takes to the rooftop to align a communicator dish; both face intense battles against alien forces. While Zhen Zhen manages to secure the basement, Alex lures an alien to a testing chamber, exploiting the equipment to eliminate the threat.
With their lives at stake, Zhen Zhen, Dariush, and Gabriel work swiftly to launch the Excalibur weapon. In a triumphant moment for the young heroes, they watch from below as the alien mothership erupts in the sky, obliterated by their efforts. The adventure culminates with Alex reuniting with his mother, as the group is hailed for their bravery in overcoming the impossible.
