At Medfield College, Dexter Riley, Kurt Russell, is a passionate young scientist who dreams big. He teams up with his friends Richard Schuyler, Michael McGreevey, and Debbie Dawson, Joyce Menges, to explore the possibilities of science beyond the classroom. Their enthusiasm catches the attention of the weary Dean Higgins, Joe Flynn, who worries aloud about the college’s shaky finances and real future. In the shadows of the same corridor, Professor Lufkin, William Windom, guides Higgins through the messy, cluttered science lab where Dexter is secretly toiling away on an invisibility experiment. The lab’s hum is drowned out by the thunderstorm that roars outside, and a strike of lightning tears through the building, damaging a good portion of Dexter’s delicate equipment. The very next day, Dexter discovers that a portion of his experimental formula has rendered part of his glasses invisible, and with a few careful tests he realizes the substance causes temporary invisibility that can be rinsed off with water.
A.J. Arno, Cesar Romero, a recently released criminal who now claims ownership of the college’s mortgage, makes a pointed appearance, reminding everyone of a darker history. Two years earlier, Dexter helped expose Arno’s gambling scheme, and now the wary student body watches as Arno hints at renewed influence over the campus. Dexter and Schuyler seize a chance to investigate by using the invisibility formula to slip into Arno’s office. There, they uncover documents proving a curious, little-known 1912 statute that makes gambling legal on college land, and they learn Arno’s plan to transform Medfield into a bustling gambling town.
Armed with this knowledge, Dexter shares his discovery with Lufkin and Higgins. Dexter suggests entering the upcoming Forsythe science contest with the invisibility serum to win the prize money needed to rescue the college from its financial brink. Higgins, however, is reluctant, pushing instead to focus on Druffle’s bumblebee study, a project he believes has safer promise. In a surprising turn, Medfield has actually been dropped from the contest. To swing the odds in their favor, Higgins seeks the sponsor Timothy Forsythe, Jim Backus, and secures a chance to rejoin. Dexter takes a dramatic step: he hides in plain sight, invisible, and subtly influences Higgins’ golf shots, producing a string of improbable hole-in-ones that stun everyone. Forsythe is won over, and Medfield is reinstated in the competition.
Arno’s keen eye doesn’t miss a moment, and he becomes wary when he notices Dexter blinking back into visibility in the shower. Suspicion grows as Higgins is invited to a high-stakes pro golf tournament and decides to take a crack at saving the school by winning big. Dexter’s plane to the event is missed, and Higgins’s performance on his own is a poor showing, leaving Arno puzzled by the strange performance he’s observed.
Back on campus, Higgins and Lufkin pivot, hoping Druffle’s bee study might still carry the day. But Druffle’s life takes an unexpected turn when he’s badly bruised after a run-in with a swarm, forcing the team to rethink their strategy. Lufkin then proposes giving Dexter’s invisibility formula another chance, and Higgins reluctantly agrees, hoping a real breakthrough might come at the last moment.
That night, Arno’s chauffeur Cookie, Richard Bakalyan, disguised as a janitor, spies on Dexter and Schuyler as they test the formula and later steals the crucial sample. When it comes time for the Forsythe demonstration, Dexter unknowingly presents the wrong (swapped) spray, and the display collapses in embarrassment, costing Medfield the chance at the prize. The theft is eventually uncovered when a janitor’s walkie-talkie—planted by Dexter—confirms that Arno intends a nighttime bank heist.
Schuyler heads to the police with the alarming information, while Dexter warns the bank’s president, both officers of the law dismissing their claims at first. Undeterred, the invisible Arno and Cookie enact the robbery anyway, triggering a wild chase. Dexter and his friends manage to force Arno’s invisible car into a swimming pool, turning the vehicle, Arno, Cookie, and the money visible and leading to their arrest.
With the danger behind them, the friends race back to the Forsythe Award ceremony, determined to salvage Medfield’s standing. The re‑demonstration goes wrong again, and Higgins proclaims that invisibility “doesn’t exist”—just as his upper body suddenly turns invisible in front of the astonished crowd. In a twist of fate, Medfield somehow wins the $50,000 prize, securing the college’s future for another year and cementing Dexter’s place as a true innovator who pushed science—and a sleepy campus—toward a brighter, if imperfect, future.
