Naina Jaiswal, a teacher at the Little Tots play school in Colaba, Mumbai, who had been on leave for three weeks, unexpectedly returns a week early. The school sits across from the property owned by Rohit Mirchandani, Naina's fiancé, where the couple lives. Parents drop off their children, and Naina asks one of the female parents to send a cake for her daughter Niharika's birthday, delivered by the parent's driver. After setting up a cartoon for the kids to watch, Naina calls the police station and informs them that she has taken 16 children as hostages. Niharika's driver arrives with a cake and Savitri, the helper, returns to the school after forgetting her phone; both are taken hostage.
The police suspect it is a hoax, until Naina fires shots in the air. ACP Catherine Alvarez contacts her, but Naina says that she will negotiate only with officer Javed Khan. Javed is brought to the scene, and she tells him that she will free one child for every demand he meets, or else she will kill each child in alphabetical order, starting with Aakash. Her first demand is for a transfer of ₹5 crore to her bank account. Catherine and Javed, who shared a romantic history, are incompatible when working together. Catherine sends armed police inside, against Javed's will. Enraged, Naina kills Aakash while being live on national television. The Commissioner of Police places Javed in charge and assigns Catherine to research about Naina.
Naina's second demand is to speak to the Prime Minister, Maya Rajguru. Rajguru talks to Naina on the phone, but Naina urges her to meet in person. Naina then tells Javed to find and bring Rakesh Mathur and Charan Kumar, from a school in Goregaon. The police capture Rakesh, but are unable to locate Charan.
During a background check, Catherine learns that Naina has been taking antidepressants and seeing a psychologist, Dr. Juneja, since she was 16. She searches Naina's house and finds receipts for medication prescribed by Dr. Juneja. Catherine contacts her, and Javed gets hold of Naina's mother Kusum, whose revelation comes across as a brutal shock to Javed; Naina was raped when she was 16, and Javed and Catherine were then officers in charge of the case. They neglected Naina's case, since they were pursuing a high-profile case to gain recognition. After begging them to help for two years, Kusum became resigned to their indifference; in the present, she blames Javed for being the root cause of the drama due to his and Catherine's inaction.
Rajguru decides to meet Naina in person, accompanied by Javed, after Naina releases Savitri along with Aakash, whom she had spared. Naina brings up the Protection of Children from Sexual Offenses Act, which protects children below the age of 18 from sexual offenses. Naina asks Rajguru why is there no protection for people over 18, and demands that her rapists face the death penalty. Rajguru tells her that legislation is a complex task that requires time, but her rapists are found and imprisoned.
It is revealed that the driver is actually Charan, who had raped Naina as a child, while Rakesh restrained her. Naina had plotted to kidnap him when he reveals that he is Niharika's driver while holding her hand, much to Naina's shock. She shoots him dead in the presence of Rajguru and Javed. Armed Commandos enter the school and arrest Naina. She is taken to prison, and later, is assigned a teacher for the female inmates, while Rajguru makes an announcement that the capital punishment for rapists will be a death penalty.
