Adolescent Ben Crandall awakens from a dream and draws the design of a rocket ship. After, he radios his friend, Wolfgang Müeller, and tells him his dream of flying. The next day, on his way to junior high school, nerdy Wolfgang is bullied by a group of boys, led by Steve Jackson. When Ben steps in and insults Steve, he, too, is targeted by the bully. After school, Steve punches Ben in the face, and a boy named Darren Woods comes to the rescue. Ben follows Darren home to thank him, and learns that Darren’s mother died when he was a child. Ben invites his new friend along to visit Wolfgang, and they are met by the boy’s eccentric family. In Wolfgang’s basement laboratory, the boys share their experiments with Darren, and Ben explains his fascination with outer space. When Wolfgang inputs the information from Ben’s dream into his computer, a strange force shoots out of the monitor, destroying a shelf of books, and the boys vow to keep their unknown experiment a secret. Later, Wolfgang invites Ben back to the lab and tells him they created an invisible force that can destroy anything. Wolfgang makes the force field visible and in the shape of an orb, explaining they can manipulate its shape and size. When Wolfgang’s cat jumps onto the computer keyboard, the orb travels into the neighborhood, causing destruction. Soon, Darren arrives, as Wolfgang frantically tries to control the orb. The mysterious force returns to the lab and smashes into a circuit box. The boys later move their experiment outdoors to a hill, out of the way of the neighborhood. When Wolfgang steps away from the controls, Ben commandeers his computer, and accidentally traps Wolfgang inside the orb. Ben fails to control the force field, and it flies across the valley with his friend inside, before it tunnels underground and reemerges in the sky. Ben removes the power cord from the computer’s mobile charger, and Wolfgang falls, laughing, onto a treetop, telling his friends the orb has no inertia inside, so he did not feel the acceleration or the impact. Darren proclaims that with seats, they could fly inside together. Ben suggests a trial run, and takes the orb to the home of his love interest, Lori Swenson. With Wolfgang at the controls, Ben is lifted to her second story window where he watches her talk on the telephone. When Lori hears a noise, Ben is sent crashing to the ground. After she calls out to him, Ben tells the girl he is rescuing a cat. Later, Darren takes his friends to a junkyard, and they acquire an old carnival ride seat, large enough for all three. While rolling the seat home, it crashes in a ravine, but they decide to return there to work on it over the next several nights. Darren steals a beer to christen the ship, The Thunder Road, and they climb inside for their maiden voyage. The ship holds together as they soar above town. However, Wolfgang loses control while hovering over a drive-in movie theater, and the ship crashes into a concession stand before launching back into the sky. Soon, they are sighted by a police helicopter, and ordered to land. When pilot, Charlie Drake, sees the boys wearing oxygen masks, the distortion makes them appear to be aliens. The boys escape at warp speed, before the computer malfunctions again, and Wolfgang declares it is controlling itself and pulling the ship into outer space. Acting quickly, he unplugs the power controls, and returns his friends safely to the ground. Ben excitedly plans their next voyage, but Wolfgang refuses another trip until he can determine where the computer commands are coming from. The next day, the boys discover that police are investigating the unidentified flying object sightings at the drive-in. Charlie Drake is haunted by what he saw, and tells co-pilot, Gordon Miller, about the strange dreams he has been having, which remind him of the dreams he had as a boy. That night, Ben, Wolfgang, and Darren share the same dream, and upon waking, Wolfgang draws a diagram of something he saw. The boys conclude the dream is a message sent from outer space. Charlie later discovers the spacecraft he saw from his helicopter in the ravine, and finds Ben’s jacket inside, with his address written on the collar. Elsewhere, Ben prepares for his next voyage, and says goodbye to his mother. Leaving home, Ben is confronted by Charlie, who reveals his jacket and asks about the spaceship. The boy runs away to meet his friends, and they quickly board the ship. Charlie follows, and as the ship takes flight, he watches with admiration, remembering his own childhood dreams of flight. Soon, the boys travel to outer space and encounter a giant alien spacecraft, which pulls their tiny ship aboard. Ben is filled with excitement, while Darren and Wolfgang express concern. Once inside, the boys explore the alien craft, waiting to meet their hosts. Darren is separated from his friends, and elsewhere, Ben and Wolfgang are examined by a metal, insect-looking device, before they, too, become separated. Wandering around the craft, Ben finds Darren and awakens him from a trancelike state. The boys explore and, at last, encounter an alien, but the slimy creature hides from them. When Ben attempts to communicate, he is surprised when the alien responds with familiar lines from television shows. Elsewhere, Wolfgang bonds with a female alien named Neek, and he introduces the flirtatious creature to Ben and Darren, who arrive with their alien friend, Wak. The boys are amused when Wak reenacts television shows, although Ben is disappointed that this is the extent of their earthling knowledge. Wak and Neek explain they have never visited Earth because of the germs, and how they would be treated if captured. They admit to sending Ben messages through his dreams so they could encounter a real human. As a larger space ship arrives and pulls their spacecraft inside, Wak and Neek usher the boys to their ship and encourage them to leave, although the boys do not understand the hasty send off. Suddenly, a much larger alien appears, and the boys learn he is the father of Wak and Neek. Ben then realizes the alien siblings are youths, like he and his friends. Before departing, the aliens give Ben a trinket, telling him it is, “The stuff that dreams are made of,” and bid the boys farewell. Arriving back home, the force field inexplicably shuts off, and they crash into a lake. Elsewhere, Ben’s love interest, Lori, awakens from a dream and races to the dock. She watches from the bushes as the boys emerge from the water, and their space ship sinks beneath the surface. Later, in class, Lori passes a note to Ben, asking about his voyage. Ben’s trinket begins to glow, and, later, in a dream, he flies above the clouds without a ship, joined by Wolfgang and Darren. Lori then appears, taking Ben’s hand and kissing him while in flight. Ben and Wolfgang wonder aloud what will happen when they awaken from their dream.