BADLA is the story of a murder accused trying to prove her innocence. Naina Sethi (Taapsee Pannu) is a successful businesswoman in London and married with a daughter. Her life turns around when she's accused of murdering her lover, Arjun Joseph (Tony Luke). All evidences are against Naina since she was the only one in the hotel room where Arjun was killed. She claims a third person was present who carried out the murder and even hurt her on the forehead.
But the preliminary investigations revealed that the room was locked from inside. Witnesses outside the room confirmed that nobody came out of the room. Naina's lawyer Jimmy Punjabi (Manav Kaul) realises that it's a tricky situation. Hence he hires expert defence attorney Badal Gupta (Amitabh Bachchan) to ensure she doesn't have to go to jail. Badal reaches the residence of Naina and he begins his own investigation.
Upon talking to Naina and insisting that she tell him the truth, a lot of skeletons tumble out of her closet. She reveals that the murder of Arjun has something to do with the disappearance of a young man from a small town of Aviemore named Sunny Kaur. What happens next forms the rest of the film.