Devki Sabharwal (Sridevi) is teaching a biology class. The class consist of her step daughter Arya (Sajal Ali), her friends Rishi and Sapna, her crush Kabir, and a boy named Mohit who also has a crush on Arya. Mohit sends a Lewd MMS to Arya in the middle of the class, and her friend draws attention to them when she reacts to it in shock. Devki, even though Arya is her step-daughter, asks the two girls to leave when they do not snitch on Mohit. But Sapna gives in and tells Devki the truth due to the fear of being punished. Devki, on seeing the MMS, throws Mohit’s phone out the window and asks him to arrange a meeting with his parents. The scene then shifts to dinner, at Devki and Arya’s house. It becomes very clear that Arya and Devki share an estranged relationship.
Arya is not able to accept her as her Mother, and Devki never fights that and loves Arya like her own daughter. There, Arya asks her fathers permission to attend a Valentines Day party at Zodiac farms, on the outskirts of Delhi. Anand, Devki’s husband, leaves for New York, where he will be staying for 10 days for some work related meetings. During the party, the trio, Arya, Sapna and Rishi, get interrupted by Mohit’s indecent efforts to get Arya’s attention. When Mohit is rejected by her, his elder cousin brother, Charles, gives it a try. Arya blatantly refuses him as well. This rubs his ego in the wrong way and he, along with another one of his loyals, decides to abduct her. The convicts, Charles Dewan, Mohit Chaddha, Joginder Singh, and Babu Ram Pandey gang rape her in Charles’ car while driving through deserted roads. They even try to kill her by strangling her, before throwing her in a nearby Gutter.
Devki on the other hand, who had been trying to reach Arya for almost 2 hours, decides to pick her up at the party. When she finds no trace or Arya, she files an FIR in a nearby station and that is where Dayashankar Kumar a.k.a DK (Nawazuddin Siddiqui) gives her his card and prompts her to reach her whenever needed. The next morning, a man walking his dog, finds and reports Arya’s situation. On seeing Arya in the hospital and receiving the news of her rape, Devki breaks down and calls Anand back home. Trials go on and the convicts get released on the basis of circumstantial evidences. Crime Branch inspector, Mathew Francis (Akshaye Khanna), who had been handling the case apologizes to the parents. But the last straw for Devki is drawn when she sees Mohit roaming freely in the school. She contacts DK, who provides her with the information of each and every rapist one by one. The first one on the list is Babu Ram Pandey.
Devki lures him out with the help of her unisex students and his favourite commodity, his manhood is chopped off. When he reaches home 4 days later, he slips and hits his head on a pipe as he realizes what has happened to him. Mathew gets a little mislead and thinks the father is to be blamed for this revenge. The next one is Charles Dewan and Mohit Chadha. Devki slips him a cyanide made from Apple seeds mixed with his whey protein shake, and frames Mohit for it, who later receives jail. Akshaye Khanna finally figures out what Devki has been doing and warns her. All of these things happening with her culprits, gives Arya hope and she decides to take a vacation with her family, to Jhonson Cottage near Kufri. The twist comes when Joginder realizes what has been happening.
He finds out through Charles meek attempts that the mother of the girl they raped is behind all this. He also figures out that DK had been her source of information and shoots him after finding out where the family is. Mathew, who also happens to be given DK’s case, finds out what had gone down and leaves for Jhonson Cottage where Joginder has planned to take down Devki. Joginder cuts the power of the cottage and kills the caretaker. As Anand goes to check out the power situation, he too is shot. When Devki sees Arya and Joginder standing in the same room, she tries to fight him off and give Arya a head start. As Arya runs out into the wild, Devki is asphyxiated by Joginder who leaves her there, mistaking her for being dead. But soon Devki regains consciousness and runs out after Joginder and Arya. Joginder, who had so far been unsuccessful in finding Arya, sees Devki and hits her with a branch. But before he could shoot, Francis reaches the spot and shoots him in the leg. This is followed by a fight sequence between Francis and Joginder, at the end of which Francis points a gun to Joginder’s head. But to his shock, Devki gets a hold of Joginder’s gun and is pointing it to his head as well. Francis convinces Devki to not shoot as he has proof and Joginder would be committed.
The moment becomes tense as the dilemma of whether to shoot or to stay with her family and not get convicted take over Devki. As Francis takes the gun from Devki, she exclaims how nothing will ever happen to such criminals. This results in a change of heart for Francis, who then gives her his own official gun to shoot Joginder. In the fear of being killed, Joginder tells Francis all that Devki had done to all the other rapists. Coincidentally, Arya had been listening to the whole conversation, hiding behind a tree. On realizing Devki’s love for her, she steps out and for the first time calls Devki “MOM”. That word does something for Devki and she shoots Joginder. The movie ends with the mother daughter hugging and realizing their affection for each other.