Three teenage friends, Timmy [Omri Katz], Mick [Shawn Hoffman], and Jamie [Tiffanie Poston], love to curl up with a goofy animated show called Dino Saurs, where dinosaurs and cavepeople share adventures on a cartoon Earth. One afternoon, eager to watch on a bigger screen, Timmy—the youngest of the trio—suggests they try the lab’s giant TV, which is hooked up to an experimental device meant to open a portal to another dimension. After they pop the videotape into the device and power it up, a swirling vortex pulls them through the screen and into the world of the show itself.
They emerge inside a building in Saur City, where they meet Forry, a friendly Rhamphorhynchus who has lost his ability to fly. Their arrival doesn’t go unnoticed for long: a group of cavepeople called the Rockies storm the place, and they work for Mr. Big [R.A. Mihailoff], a harsh dictator who keeps the residents of Saur City under his rule. The Rockies steal a fuse that powers a cooling system for lava tanks. Without this fuse, the lava will melt the city’s defenses and threaten everyone, and the kids realize they also need it to reopen the portal back to their own world.
Forry’s knowledge of this world proves invaluable as the trio and their new ally navigate a dangerous landscape filled with ancient ruins and strange towns. They pass through a dinosaur graveyard and eventually reach Tar Town, where they step into a bare-bones bar and meet Rex, a mighty Tyrannosaurus, and Tops, a stalwart Triceratops. The two legendary heroes of the show initially refuse to help the newcomers, but their stance softens after Timmy, Mick, and Jamie lend a hand in fending off the Rockies, proving they deserve a chance.
Back in Saur City, the group makes camp in Forry’s tree house. Timmy ponders the idea that stories from fiction might exist in other worlds, hinting that he could stay if his own world feels dull. Romance threads begin to show between Mick and Jamie, adding a light, human note to the peril around them. Rex takes Timmy aside to reveal a painful family secret: his father was betrayed and forced to surrender Saur City to Mr. Big. When the friends return to the tree house, they are ambushed by the Rockies again, and Timmy discovers a remarkable power—his remote control from the lab can pause and rewind the Rockies’ advances. Mr. Big spots the display of power and orders the Rockies to seize the remote, carrying Timmy off toward his looming tower.
The remaining friends—Mick, Jamie, Rex, Tops, and Forry—stage a daring rescue by sneaking into the tower’s dungeon. They free Rex’s imprisoned father, who explains that Mr. Big used a mind-controlling potion to bend the ruler’s will and secure Saur City’s surrender. A skirmish erupts as Rex confronts Mr. Big, while Mick and Tops work to pull Timmy free and reclaim the remote. The heroes recover the device, and Rex fights valiantly, nearly beating Mr. Big until the villain wields a sword. In a final surge, Timmy uses the remote to zap Mr. Big, causing him to vanish from the tower in a puff of magical energy.
With the danger temporarily gone, the team discovers the elevator’s power source—dependent on the fuse. Forry stays behind to snag the fuse and get it to safety while the others descend. Rex’s father makes the ultimate sacrifice to destroy the tower, sacrificing his own safety so the city might live. The fuse is reattached to the lava tanks, and Timmy uses the remote one last time to reopen the portal to their home world. The youngsters hesitate at the thought of leaving but finally step back through the portal just as Timmy’s parents return from a scientific conference.
Back in their lab, Timmy’s family is brought into the whirlwind of memory and possibility, and the device hums to life once more—an echo of the extraordinary adventure they’ve just lived, waiting to be told again as the tale continues.
