Spencer Griffith, Joseph Mazzello, is a shy seventh-grader who secretly harbors a crush on Michelle Eberhardt, Lauren Eckstrom. One night, a mysterious meteor crashes into a nearby junkyard, and Spencer sneaks out to investigate. He discovers that the meteor is actually a small rocket carrying a Cybersuit, a prototype exoskeletal suit with artificial intelligence from another galaxy, Arthur Burghardt and Alex Daniels providing the voices. After trying it on, he needs a moment to adjust to the jaw-dropping speed and strength, and he affectionately names the suit “Cy.”
With Cy, Spencer begins to test its many functions and soon decides to use it to shape his own upended night. He starts by getting back at bully Manfred 'Turbo' Bruntley, Joey Simmrin, then saves Michelle, Lauren Eckstrom, and her friends from a damaged Rock-O-Plane, even toodling through a fast-food drive-thru to satisfy his curiosity. The new power also leads to some comic misadventures at home—he bangs his head in a refrigerator and discovers the odd, unappetizing ways Cy can help him eat his take-out, and even figures out a peculiar, humorous way to pee when he can’t get out.
Meanwhile, Earth is visited by a Broodwarrior, a member of an insectoid alien race waging war against Cy’s creator, Tenris De'Thar, and his fellow Trelkins, who built Cy as a weapon to tilt the war in their favor but were forced to launch it into space. The Broodwarrior’s mission is to locate and capture Cy so his race can study it. Spencer barely escapes when the Broodwarrior first arrives, and he eventually releases Cy, retreating and leaving the alien to its pursuit. Back home, after a moment of inspiration from a comic book titled MidKnight Warrior, Spencer weighs what the hero would do in his situation and steels himself to act.
He unexpectedly finds an ally in Turbo, who gradually becomes a real friend, and together they head back toward the junkyard where Cy lies in danger. The Broodwarrior has already taken Cy off-world, and the two friends devise a plan to distract the invader long enough for Spencer to rescue Cy. A brutal battle ensues, with Cy taking heavy hits—its damage mounting as the Broodwarrior closes in. Spencer fights on, covers Cy with scrap metal to shield it, and even uses a piece of the wreckage to keep fighting. The Broodwarrior presses the attack, chasing Turbo, and Spencer ends up cornered inside a junked ice cream truck. In a dramatic trap, Turbo activates the car crusher, and the truck is crushed into a solid cube, killing the Broodwarrior.
With the Broodwarrior defeated, Spencer and Cy return to the scene, only to discover Cy isn’t beyond repair after all. Tenris De'Thar, Larry Nicholas–as Tenris and other Trelkin soldiers appear from a giant UFO orbiting Earth and quickly repair Cy, reviving it. After saying goodbye to Cy, the head alien soldier presents Spencer with a badge for his bravery and courage before the travelers depart for their home world. The long, eventful night ends, and the next day at school finds Spencer now more confident, with Turbo’s friendship guiding him as he starts a conversation with Michelle, stepping forward into a brighter, self-assured future.
