Don Quixote (Amrish Puri) is a don who plans on selling India in a widely publicized auction. His plan is simple; kidnap the president of the country (Anupam Kher), replace him with a lookalike (also Anupam Kher), threaten mass chaos and violence, enabling the fake president to hold the country at ransom, and finally selling it altogether.
Hero (Shahrukh Khan) is new to Mumbai, penniless and desperately seeking employment. Miss India (Deepa Sahi) is having the time of her life after her success as a model, on the night she meets Hero. They meet and decide to spend the night entertaining each other, in any way possible–joking, dancing and doing whatever spontaneously comes to mind.
Meanwhile, Don Quixote's son, Prince (Javed Jaffrey) has set his eyes on Miss India, who thwarts all his overtures. The night turns out to be an adventurous one for Hero and Miss India. Hero discovers that Miss India's father is a drunkard, who wants her to enter prostitution, while Miss India discovers that Hero has brain tumor. When they find out Quixote's plans, they decide to save the president.
In the ensuing chaos, Quixote is killed and Prince takes his throne. Prince decides to continue his father's plan. Some people previously rescued by Hero and Miss India kill the fake president. Prince suddenly makes an entry with his henchmen. Hero, Miss India and their friends successfully overpower the cronies, while Hero kills Prince.
Finally, Hero makes a makeshift parachute and jumps from the building with Miss India. During the jump, Hero declares that he is glad to be alive. When Miss India reminds him that he has brain tumor, Hero tells her that the X-ray she saw was taken eight years ago!