An F-15 Eagle takes off on a mission to locate a target over 50 meters tall in the city below. Flying low, the jet becomes easy prey for a colossal gorilla who swats it from the sky with a single, devastating swing.
One week earlier, an alien ship crashes in the Amazon. A local tribe seizes the ship’s power source, prompting General Mills, John Migliore, to dispatch famed tracker Skipper Smith, [Peter Whittaker], and his assistant Marion Kind, [Candice Lidstone], to recover it. To Skipper Smith’s delight, the tribe’s members are all women. Distracted, he and Marion are easily abducted and brought before their queen, Peggy, Christie Emes, who wears the power source as an amulet. She shows them mercy, allowing them to stay for the night. Smith seduces her, convincing her to take off the amulet, then dashes away with it. Marion calls in a seaplane, and they bring the artifact to Professor Mills, John Migliore. He dubs the substance inside it KTNT and attempts to splice its DNA with that of a houseplant, with dismal results. Next he experiments on a monkey, who puts up a fierce fight before taking the KTNT in pill form. As he observes the results, two terrorists break into his facility. He sets the monkey free, but they shoot him before he can destroy his research.
Fleeing to the suburbs, the monkey rests in a shed. The general is informed of his brother’s death and the theft of the alien technology. He orders a search for the escaped test subject, calling back the retired Major Bummier, [Trevor Payer], into the field. Two boys, Chance, [Chance Kelly], and Grayson, [Grayson Kelly], discover the monkey after he eats their snacks. Naming him Konga, they agree to keep him a secret from their mother, Mom, [Anne-Marie Frigon]. Bummier, traveling door to door, asks a neighbor if she’s seen an escaped ape. The boys play in their backyard with Konga, who suddenly grows to enormous size and rushes past Bummier.
Konga terrifies a farmer before growing again, bursting through the roof of his barn. Spotting a beautiful blonde woman in her bedroom, he abducts her just to give her a kiss on the head. In Jackson Park, all of the fleeing citizens start to depress him. Moving downtown, his clumsiness causes mass destruction, toppling buildings and cooling towers. A passing airliner catches his attention, and he snatches it out of the sky. Chance tries to lure him away by dressing up as a hot dog, but the military nonetheless assails the monster with tanks and fighter jets. Suddenly, Konga returns to his original size, and the boys embrace him. Charmed, the general reports to Mills that Konga escaped, and announces his second honorable discharge. Professor Mills, alive, explains to his brother that Konga’s body eventually rejected KTNT, allowing him to shrink. Another drop of KTNT allowed him to survive being shot.
In a post-credits scene, Chance and Grayson discover a large egg in the woods.
