Three childhood friends, Alex, Tuck, and Munch, are facing the impending demolition of their small Nevada neighborhood due to an upcoming highway construction project. The day before their relocation, mysterious patterns appear on their phones, which Munch discovers lead to coordinates in the nearby desert. Eager for adventure, they decide to spend their final night together exploring these coordinates, documenting their journey with smartphones and video cameras.
Upon arriving at the coordinates, they find a dusty, rusted object hidden beneath an electrical tower. As they take the object with them, they follow another map that leads to a nearby barn. To their astonishment, the object begins to telekinetically repair itself, using items from the barn. The boys soon uncover that the object contains a cybernetic alien capable of answering yes or no questions. The alien reveals its origin from another planet and recounts its crash landing on Earth after being shot down, sustaining serious injuries in the process. Following yet another map, they head to a pawn shop where the alien continues its repairs. Due to damage to its eyes, it ingeniously uses Alex's phone camera to see. As they depart the pawn shop, the group decides to name the alien Echo.
Their adventure continues as they follow the next map to the house of Emma, a classmate who stumbles upon Echo and joins the trio. They make another stop at an arcade, where Alex faces a dilemma when he is caught by a security guard. With Emma risking her safety to rescue him while Echo creates a diversion, they manage to escape. Later, while dining at a restaurant with Echo hidden in a backpack, a construction worker unwittingly steals the bag and loads it into a truck. Munch, ever resourceful, jumps into the truck just as it drives away, leaving the rest of the friends behind. To reunite with Munch and Echo, Alex and Emma assist Tuck in "borrowing" his brother's car, driving off towards the construction site where their friends are held captive.
In a tense encounter, they infiltrate the site, only to get caught by the same construction worker, who is revealed to be Dr. Lawrence Masden. This scientist reveals his intentions to capture Echo for scientific exploitation, admitting that he was part of the group that shot the alien down. He tries to manipulate the kids into believing that if Echo repairs the key to his spaceship and departs, it will result in catastrophic consequences for the neighborhood. The clever kids feign agreement, promising to assist Masden in locating the spaceship if he allows them to rescue their friends.
They are taken to a scrap junkyard, where Echo appears to succumb to the harsh experiments. However, encouraged by the children's spirited support, he revives, completes his repairs, and creates a diversion allowing the kids to escape back home. Once at Alex's house, they watch in astonishment as the spaceship key mysteriously inserts itself into the ground, revealing that the agents had concocted the false construction project to excavate the neighborhood for the alien ship hidden beneath.
Placing their trust in Echo, Alex descends into a tunnel created by the key. At the bottom, they discover a room containing the spaceship's core, where the key links it to all its components. After connecting the key and allowing Echo to activate the ship, they bid farewell and exit the core. In a spectacular display, the ship's parts rise from the ground and gracefully assemble mid-air, all while preserving their neighborhood intact. Once fully reconstructed, the ship launches into the sky. Despite the project being abandoned, Alex and Munch are forced to relocate as their families seek new homes, while Tuck chooses to stay. As new residents move into the neighborhood, a pivotal reunion takes place sometime later, with Alex capturing a moment skyward with his phone.
In a captivating post-credit scene, Alex addresses his friends as his phone starts to move and glitch, hinting at the enchanting possibility that Echo has returned once more.
