Ezhil is a civil engineer who leads a normal upper-middle-class lifestyle. His life goes in the right direction with his construction business doing well. He is in love with a film journalist Deepika.
Ezhil’s lookalike Kavin is an intelligent, street smart, conman who swindles money from smugglers, woo multiple women, and knows all the loopholes in the legal system. His only weakness is gambling which he inherited from his mother who got divorced from her husband when the kids were young.
Both of them travel in their own paths until a man named Akash is murdered and Ezhil is nabbed by Inspector Gopalakrishnan based on his image which was found in a selfie pic taken by the neighbour of the victim. Gopalakrishnan (who wants to frame Ezhil for personal reasons) asks his assistant, the smart Malarvizhi to investigate the complicated case. Coincidentally, cops also arrest Kavin in a drunken drive case and he is brought to the same police station. Both Ezhil and Kavin deny their involvement in the murder, creating confusion among the officers. On the advice of his PP, the Inspector illegally keeps both of them for questioning over the weekend.
After scouring Akash’s house for evidence, the forensic department finds a single strand of hair and send it to the lab for testing. However, it turns out that since Kavin and Ezhil are identical twins, their DNA is the same and hence it is impossible to identify the culprit. Meanwhile, Suruli is interrogated by the police but is let go since he claims he wasn’t feeling well that day. As there is no progress in the case, the police go back to Akash’s house to find a clue.
Unknown to anyone, the murderer had left a fingerprint on the wall of the house, which is unfortunately erased by one of the constables. Back in the station, both the brothers encounter each other as Ezhil tried to escape and they beat each other brutally, which is witnessed by the police. Having no other way to find the culprit, the police decide to dig into their past.
In flashbacks, it is revealed that Kavin and Ezhil’s parents were divorced and their mother was a gambling addict who would lose her salary on gambling. She kept claiming that she would stop, but she didn’t. At one point, she promises on Kavin, but when she loses his trust, she commits suicide. Kavin is brought to live with his father and Ezhil, but they don’t feel comfortable with him. At one point, Kavin starts gambling and develops bad habits. When his dad confronts him, a fight breaks out between Kavin and Ezhil, after which Kavin leaves.
After many years, Ezhil sees Kavin exiting his house and discovers a ring he was going to give Deepika is missing and assumed that Kavin had stolen it. Kavin is brutally interrogated by the police, but it turns out that it was in Ezhil’s drawer and Kavin swears revenge.
On the night before Kavin and Ezhil need to be produced before the court, the inspector gets some information and leaves. It is revealed that on the night of the murder, a jewelry shop was robbed and he assumes that Kavin was the robber, as he had to settle a debt, which would pin Ezhil as the murderer. However, Kavin says he won the money by gambling, which is confirmed by a Marwadi Seth, so the inspector confirms it is Ezhil who is the murderer. However, a constable says that the murderer is Kavin, as the taxi driver who helped Ezhil when his tyre got punctured had come to confirm Ezhil’s alibi.
As both have air-tight alibis, both the brothers are acquitted.
However, it is revealed that Ezhil got information from Deepika’s friend that she had gotten off the train with one of her school classmates, revealed to be Akash. On the night of the murder, Ezhil had gone to confront Akash who reveals he was on the train and that he had spiked Deepika’s drink and had raped her for 2 days before he killed her. In a fit of rage, Ezhil brutally stabs and kills Akash with a screwdriver and burns all the evidence. Malar figures all this out and is shell-shocked. The report from the mental hospital where both the brothers claimed the latter was admitted arrives and it is revealed that both the brothers were admitted (Ezhil for 3 months and Kavin for 1 year). The last line in the report says that even though both the brothers despise each other, they come together when there is a problem.
It is revealed that Kavin had been following the case and manipulated Malar to shift her focus from Ezhil to him. Malar realizes that if she reveals the truth, her job is at risk, since she had arranged for a false witness (the taxi driver), so she doesn’t say anything. The film closes with both the brothers parting ways, with Ezhil going to settle in Copenhagen and Kavin going to marry Ananthi, leaving his old life behind. A mid credit scene reveals the true events, where identical twins were acquitted under similar circumstances.