A series of child abduction and murders have left the police force perplexed who are unable to solve the case. Hence the case is handed over to CBI, who designate trainee Reet Oberoi (Preity Zinta) to solve the case. After some investigation the evidence points towards Lajja Shankar Pandey (Ashutosh Rana), a religious fanatic who believes in the sacrifice of children to gain immortality. Pandey's erratic behaviour and Reet's traumas (as a child she witnesses her older brother, a terrorist, being gunned down by the police in their home) forces Reet to seek help from a prisoner, an unjustly implicated genius by the name Professor Aman Varma (Akshay Kumar).
At first he's rude towards Reet and refuses to help her, but with some help she manages to sway him into helping her. The case gets even more tough as she finds out that the Home Minister's only child has been kidnapped by Pandey. Reet cannot handle the pressure alone due to her traumatic childhood and her phobias, also she faces opposition from the local police partly because of Varma's methods. As they begin to spend more time together, he helps her overcome her fears and they both fall in love with each other.
They eventually track down Pandey, who is about to begin the last sacrifice on the day of a solar eclipse (Soorya Grahan) which will finally help him attain the unattainable Immortality. Aman and Reet eventually save the child, killing Pandey in the process, but Aman is seriously hurt and is on the brink of death. Reet and Aman share a last kiss and he dies in her arms. Reet is given a hero's welcome and she finds a new sense of life in herself.