Indian Army officer Lieutenant General Nikhil Bakshi addresses a group of Indian soldiers aboard the INS Viraat, detailing a woman's exploits while serving as an undercover agent of the Research and Analysis Wing (RAW), India's external intelligence agency, in Pakistan.
The story flashes back to events preceding the Indo-Pakistani War of 1971. Hidayat Khan is an Indian freedom fighter and agent posing as an informant for the Indian government against Pakistani government. He wishes to make his 20-year-old daughter Sehmat an agent and continue the family tradition of being in service to the country before his impending death from lung cancer. Sehmat is willing so she is trained by senior RAW officer Khalid Mir and his assistant, a young Bakshi. Khan uses his friendship with Brigadier Syed of the Pakistan Army to get Sehmat married to his younger son, Iqbal Syed, another military officer. After migrating to Pakistan, Sehmat settles into her married life, adjusts to a new country, and establishes the trust of her in-laws. Brigadier Syed is promoted to Major General, which results in crucial documents and members of the country's defence forces passing through his house. Sehmat establishes communication channels with her handlers back in India and starts relaying information. Meanwhile, she falls in love with Iqbal and they consummate their marriage.
Sehmat spots information related to the planning of an offensive against India and is able to pass it on. One of the servants, Abdul, discovers the truth about her and Sehmat runs him down with a car to avoid exposing her cover. The event takes a heavy emotional toll on her. The information points to the planned attack on the Indian aircraft carrier INS Vikrant, then deployed in the Bay of Bengal. Sehmat reluctantly kills Mehboob Syed, Iqbal's elder army officer brother after he finds her suspicious. She is distraught at having widowed Munira, Mehboob's wife, and saves her from police interrogation. She is eventually discovered as a spy by Iqbal, who is heartbroken by the revelation. He confronts her but dies from a grenade. The grenade was thrown by a member of Mir's team to kill Sehmat should she be caught. Sehmat is alive; the woman Iqbal confronted was actually another burqa-clad agent who switched places with Sehmat and died by the grenade along with Iqbal. Shocked by her husband's death and the fact that Mir was willing to kill her, Sehmat realises the insignificance of relationships and humanity in this line of work. Broken by the destruction of a family by her hand, she returns to India and discovers that she is pregnant with Iqbal's child. She decides to keep the child.
With Sehmat's findings, the INS Rajput sinks the Pakistani submarine PNS Ghazi off Visakhapatnam's coast.[N 1]
Nikhil Bakshi concludes his speech, with Samar Syed, Sehmat's son, among the officers. Meanwhile, an aged Sehmat is seen sitting in her chair and staring out of the window of her house in the middle of nowhere.
