George States (Jeff Doucette) is suffering from the last stage of brain cancer and has only six months to live. In order to prevent death and gain immortality, he decides to extract the 'Nagmani' from a shape-shifting snake who can take human form, Nagin (Mallika Sherawat). He captures the nag [the male snake] so that the nagin [the female] comes after the capturer to free her lover, thus allowing him to obtain the nagmani by force. He keeps the nag in a glass box where he electrocutes and tortures him. His plan works and the nagin starts following him. On her way, she is helped by a police inspector (Irrfan Khan) and his wife (Divya Dutta), who is infertile, causing a strain in their relationship. The nagin also helps a few women who are helpless: One who is beaten mercilessly by her husband; one being raped by a man and so on. She brutally murders those men who were involved in the capture of her mate as well as men who torture women. The police inspector who is trying to help her find her mate investigates the murders. Finally, she reaches George's hideout where she reclaims her mate and they engage both in sexual intimacy. George attempts to capture the nagin during intercourse since this will be when she will be at her most vulnerable. Wearing a suit that hides his heat signature, he lures her by using her dying mate as bait to a trap. He captures her and tries taking the nagmani but at that moment, the police inspector arrives and helps her. Angered by the death of her mate by the hands of George, she takes on a huge form: half snake, half woman, and throws him in the same glass box where her mate was kept and electrocutes him.