Synopsis is based on the original version (made by same writer-director, in Tamil). There may be minor changes in the screenplay.
Sanjay (Aamir Khan) suffers from a short term memory loss and he can remember things for only 15 minutes. So, information he finds useful is tattooed on his body.
Chitra is a student, who needs to find an interesting patient for her college project. When Chitra locates Sanjay, she finds about his love life with Kalpana (an actress / model) from his personal diary. She also finds about who Sanjay really is, how he is in this current state and that he is looking for the person who is responsible for this situation.
Chitra wants to help him in any possible way and also find out the missing clues in the story, as well as what happened to Kalpana.