Akira Sharma (Sonakshi Sinha) is a little girl who lives happily with her father and mother. One day, she witnesses a crime involving a group of unruly men throwing acid on a young woman's face. Akira helps the police catch one of the criminals. Akira's father enrolls her in a self-defense class.
On her way home one day, Akira notices some gang members teasing a girl. She beats them up, but one of them takes out a bottle of acid to throw acid on her. When it backfires, Akira is accused of throwing acid on his face and is sent to juvenile jail.
Fourteen years later, Akira has grown into a brave young woman, while her father has died. Akira and her mom move in with her brother. Akira later joins college and lives in a hostel. A couple of students try to bully her but end up learning the hard way to not mess with her.
One night, ACP Rane (Anurag Kashyap) runs into one of the college professors with his car and beats him up because the professor is upset about his behaviour. The college students reach out to the commissioner. The police brutally beats them up and tries to move all of the students away, with only Akira remaining. She hands over the signed petition sheet and the information to the commissioner when he arrives.
A couple of days later, Rane robs and kills a man. When he admits this on the phone at his girlfriend's place, she records his confession and decides to show it to her friends. At the last moment, her camera with all the information is stolen, and someone blackmails Rane. All this makes him nervous and he kills his girlfriend and begins searching who is behind this. The case is handled by SP Rabiya, (Konkona Sen Sharma) who suspects that Rane's girlfriend did not commit suicide, but had been murdered.
One day, Akira finds a bag full of stolen items, including the camera, in front of her dorm. The associates of Rane see her and take her away and decide to kill her. She sees three of associates of Rane kill two other men. Rane calls them and tells them they have the wrong girl, but orders to shoot her. She escapes, goes to her principal, and tells him everything.
Suddenly, the associates of Rane take her away to a mental asylum, and, with the help of a doctor, they give her shocks and injection to prove that she is mentally unstable. She flees from the hospital with the help of another patient, Rani. She decides to prove her innocence by kidnapping one of the associates of Rane. Later Rane trace her hideout.
They try to kill her, but Rabiya arrives at the right moment with orders to arrest Rane. Rabiya seizes the arms from Rane and his associates. She, however, is stopped by the commissioner because Rane killed the brother of a strong North Indian politician and he will cause riots if he knows that a policeman was involved. Rane gets back charge, after the commissioner orders him to take Akira to a mental asylum. The helpless Rabiya leaves after explaining the whole thing to Akira but quietly carries along the seized arms. Akira kills Rane and his associates but still goes to the mental hospital.
Rabiya gets frustrated at her helplessness but succeeds in not registering a case against her. Akira is released three months later and decides to follow her dad's footsteps by teaching challenged kids.