Imagine being one of the most successful businessmen in the country. Sanjay Singhania (Aamir) is a rich businessman who owns a cellular phone company. Kalpana (Asin) is a model who brags to her friends and peers that she is the love interest of Sanjay, though in reality she doesn't even know the man.
When Sanjay comes to know about this anonymous admirer of his, he decides to dispel her delusions. But on his way he sees a beautiful woman helping the handicapped kids cross the road. Instantly, Sanjay falls for her. Later, he comes to know that she is Kalpana, the same model who boasted of being his girlfriend.
Sanjay gets introduced to Kalpana but doesn't disclose his real identity. Love blossoms between the two.
While on a train ride, Kalpana saves a group of young girls from a rowdy bunch of eve-teasing goons. A few days later, the same group of eve teasers, led by their notorious head (Pradeep Rawat) close in on Kalpana. But Sanjay arrives and fights them. In the ensuing scuffle, Kalpana is killed and Sanjay is hit on his head with an iron rod.
Though Sanjay is able to survive the injury, he loses his memory. He gets only flashbacks of what really happened and his short memory makes it difficult to remember things he did just minutes back.
How this man, who can't even remember the killers of his ladylove, goes about taking his revenge is what the remaining story is about. Jiah Khan plays a medical student who helps Sanjay find the killers.