Koi... Mil Gaya is sci-fi action drama about Rohit Mehra (Hrithik Roshan) who due to a childhood disorder is unable to keep pace with the grown-ups so he enjoys the company of children less than his age. His father had left back a computer which could connect to the outer world aliens but dies before realizing his dream. Rohit breaks into his father's computer after years and connects with an alien who is left back on earth. The alien becomes friendly to Rohit and bestows all his powers to him and thus follows Rohit transformation into a superhuman being.