John Brown is a humble, but clumsy security guard working at the Bradford robotics laboratory in Riverton, Ohio, run by Artemus Bradford and his daughter Brenda, whom Brown has a crush on. Brown wishes to become a police officer, with support from his niece Penny. Brenda and Artemus create a lifelike robotic foot as part of the Gadget Program, to create cybernetically augmented police officers. Tycoon Sanford Scolex attacks the lab, steals the foot, and has Artemus murdered before escaping in his limo. Brown chases him down in his car, which leads to it being destroyed by Scolex's explosive cigar, leaving Brown for dead, but a bowling ball coming from the fiery blast of Brownâ??s destroyed car crushes Scolex's hand, forcing him to replace it with a mechanical claw.
Brown survives the explosion and becomes the first test subject for the Gadget Program, as a cyborg with countless gadgets he can activate by saying "Go, Go, Gadget". Under Brendaâ??s guidance, Brown becomes Inspector Gadget. Scolex creates the alias "Dr. Claw" and uses the stolen technology to create his own robot for global domination, aided by his minions Kramer and Sykes, but the attempts fail. Much to the irritation of Chief Quimby, Gadget joins the police department, aided by his talking advanced car, the Gadgetmobile. However, Quimby refuses to give Gadget the Bradford case and instead assigns him to mediocre jobs, prompting Gadget to secretly investigate the case himself. Examining the evidence, he finds a connection to Scolexâ??s company, which Brenda has now gone to work for. Breaking into Scolex's lab, he locates the foot but is taken captive by Scolex, who discovers Gadget is powered by a processor chip, which Scolex removes, and has Sykes dump Gadget in a junkyard. Scolex unleashes Robo-Gadget, an evil replica of Gadget, who goes on a rampage across Riverton. Brenda, Penny, her dog Brain, and the Gadgetmobile track Gadget to the junkyard but find he is unresponsive. Penny believes her uncle doesnâ??t need the chip to live, which is proven when Brenda kisses Gadget, reactivating him.
After dropping Penny and Brain off at home, Gadget, Brenda and the Gadgetmobile give chase to Scolex's limo. Gadget and Robo-Gadget battle on top of the roof but are knocked off, continuing their fight on a bridge until Gadget pulls a cord on his counterpartâ??s head, causing it to fall off. Gadget then chucks Robo-Gadgetâ??s head into the river while the headless body runs off. Brenda is taken captive by Scolex, who tries to escape with her in a helicopter, only to be confronted by Gadget, who arrives using his helicopter hat.
Scolex snags Gadget on the helicopterâ??s landing gear, suspending him in midair. Gadget uses a projectile pencil to disable Scolex's claw, allowing Brenda to leap out the helicopter onto his back. They fall to the ground but Gadget saves them using an umbrella. Scolex parachutes down but is trapped by the Gadgetmobile. The police arrive, believing Gadget was responsible for the destruction, but Penny arrives with a guilt-stricken Sykes who surrenders the foot and admits to Scolex's plans. Gadget earns respect from Quimby, and departs with Brenda and Penny, though Scolex promises revenge on his nemesis. In the end credits, several afterscene clips play, including Sykes going to a minion-recovery group, and the Gadgetmobile addresses the audience till the end of the credits.