The film starts with Sona Mukherjee (Jacqueline Fernandez) having a video call with her husband Mrityunjoy Mukherjee aka Joy (Manoj Bajpayee) wherein Sona tells him that she is pregnant. Right after the video call, inspector Imran Shahid (Mohit Raina), who is also the ex-husband of Sona, visits her house to collect evidence against Joy in a serial killing case. Sona however thinks Shahid is just trying to frame Joy to take revenge on him for taking away his love. Mrs. Serial Killer 2020
The serial killing case is that of six girls in the town who went missing, and later their bodies were found in an isolated house owned by Joy. All the missing girls were unmarried, pregnant, and were aborted and dismembered. Joy, who is also a gynaecologist, is therefore arrested. The respect of people of the town for Joy turns to anger.
Sona, who firmly believes that Joy is innocent and framed by Shahid, visits Joy in prison, and Joy tells her to ask a famous lawyer Mr. Rastogi (Darshan Jariwala) for help, whom he saved before. Rastogi suggests that they should by all means get Joy bailed. But the bail application is later rejected by the court for all found evidence is against Joy. He then suggests Sona to prove Joy’s innocence in an illegal way – to kill one more girl in the exactly same way the previous 6 were killed, to prove that the killer is not Joy.
Sona is a kind person and unwilling to do anything illegal, but she finally agrees with the plan after she is convinced there’s no other way to prove Joy’s innocence. Sona chooses her neighbor Anushka Tiwari (Zayn Marie), an unmarried pregnant girl. Later, news of Anushka’s death reaches police, making the court believe Joy is not the killer and grant him bail. After Joy returns home, Sona shows him Anushka, who is still held captive by Sona. It is revealed that Sona actually didn’t kill her, but found an unclaimed body and dressed it and made it up, to make it look like Anushka’s body.