Koi... Mil Gaya

Scientist Dr. Sanjay Mehra has created a supercomputer from which he sends variations of the syllable om into space, hoping to attract extraterrestrial life. When he receives a response, his colleagues ridicule him. While driving home, an alien spacecraft appears overhead shortly after responding to his signals through the computer. Distracted, he is involved in a car accident that kills him in an explosion and injures his pregnant wife, Sonia. As a result, their son Rohit is born with a developmental disability. Sonia learns that surgery is the only cure for Rohit's disability, but it could paralyse or kill him. Not wanting to lose her son, she raises him in Kasauli.

Years later, a grown-up Rohit is still in school due to his disability, but has found companionship among six children. A young woman, Nisha, arrives and is initially insensitive towards Rohit because of the childish practical jokes he plays on her, as well as her ignorance of his mental condition. Her friend Raj, who also happens to be Rohit's former classmate, attacks Rohit with his gang, resulting in them breaking his kick scooter. Sonia scolds them for assaulting Rohit, explaining that he did not intentionally make fun of Nisha, and reveals Rohit's condition to her.

Realising her mistake, Nisha gifts Rohit a bicycle and introduces him to her parents, who are sympathetic towards him. Rohit and Nisha, now friends, discover Sanjay's old computer, and Rohit inadvertently summons the aliens. The aliens leave hastily, accidentally leaving one of their group behind. Rohit, Nisha, their group of friends, and Sonia befriend the alien, naming him Jadoo, and discover his psychokinetic abilities.

Raj resents Nisha's closeness to Rohit, bullying him and spreading a rumour that he and Nisha are getting married. The rumour upsets both Nisha and Rohit, who is hurt because he believed Nisha was his girlfriend. Jadoo discovers that Rohit is disabled and uses his powers, derived from sunlight, to enhance Rohit's mental and intellectual abilities. The next morning, Rohit develops clear vision. Although only a seventh-standard student, he solves a tenth-standard mathematics problem orally, surprising both his mathematics teacher and the school principal. He also answers questions posed by his computer teacher, who had previously mocked him for his disability, and accidentally beats up Raj's gang as well.

Rohit's physical abilities increase to superhuman levels. Raj's gang challenge Rohit and his friends to a basketball game. Rohit scores several baskets, but Raj's gang begin to cheat. When the sun emerges, Jadoo helps Rohit's team win the match. Rohit confesses his love to Nisha, and she reciprocates. Raj's gang later confront Rohit's group about the basketball game. While fleeing, the group accidentally drop Jadoo. Constable Sukhwani sees Jadoo inside a bag and calls for backup. Led by Inspector Khan, the police capture the bag; however, Rohit rescues Jadoo. Confronted by Raj's gang, an enraged Rohit overpowers them before the police arrive. Jadoo is not in the bag, having escaped while Chelaram was calling the other officers.

Suspicious of Rohit, Khan confronts him at his house with several other officers. The police seize Jadoo and knock Rohit unconscious. When he regains consciousness, Rohit catches up with the police vans in time to prevent Jadoo from being sent to the United States. The flying saucer summoned using his father's computer returns, and Rohit bids an emotional farewell to Jadoo. After Jadoo leaves, Rohit reverts to his former self; this saves him from prosecution by the government, who congratulate him for his actions.

Raj's gang later harass Rohit and Nisha, challenging Rohit to kick a ball towards them. He angrily kicks the ball into Raj's face and realises that Jadoo has permanently restored his superhuman abilities. Rohit and Nisha thank Jadoo and get married.