Parthiban is a mild-mannered cafe owner in Kashmir, who fends off a gang of murderous thugs and gains attention from a drug cartel claiming he was once a part of them.

Parthiban lives a simple life in Shimla along with wife Satya and two children and runs a cafe.Few contract killers enter the town an create havoc,one night they attack Parthiban's cafe and all get shot dead by him while trying to save his daughter and employee.The trial goes in court and Parthiban is set free as all men were criminals and he did it in self defense.Parthiban becomes a hero in town and his news is published in various newspapers where few want him dead.Harold Das one of the gangsters comes across his picture and identifies him as Leo Das who was termed dead many years back.Harold informs his elder brother Antony Das a menacing gangster who travels to Shimla to meet Parthiban.Antony is confident that Parthiban is Leo and tries all kind of ways to harass him.But Parthiban is adamant that he is not Leo and that he could be his lookalike.—alex.mjacko@gmail.com

Parthiban "Parthi" (Vijay) is an animal rescuer and cafe owner in Theog, Himachal Pradesh, living with his wife Sathya (Trisha), teenage son Siddharth "Siddhu" (Mathew Thomas) and daughter Mathi "Chintu" (Iyal). One day, Parthi's friend, Joshy Andrews (Gautham Vasudev Menon), a forest ranger, calls him to help tame a spotted hyena threatening the townsfolk. The hyena is a rabid hunter and has already attacked several humans. Nobody is able to catch it or bring it under any sort of control. The local police refuse to help and are content being observers to the mayhem being unleashed by the hyena.

With Siddhu's help, Parthi manages to tranquilize the spotted hyena which are considered to be extremely ferocious. Parthi knows that hyenas are social animals, so either this hyena lost its way, or the rest of his tribe are dead. He purposely avoids public attention over this incident and adopts the hyena after it calms down. Parthi runs a cafe called "Bold Street" in town and leads a peaceful life with his family. He is an outsider to the area and people say that he is from Chennai. Parthi names the hyena Chakadbangadu.

One night, Parthi and Chintu are at the cafe when Shanmugham (Mysskin), a robber, and his men arrive to rob it. Shanmugham and his crew had recently robbed a home and killed all its inhabitants. The house belonged to a district collector and Shanmugham had murdered his entire family on contract. One of his gang members (Sandy) found a little girl hiding inside the house, and proceeded to brutally sexually assault her, and kill her before leaving the house. As the collector is a high-profile official, Shanmugham and his crew sought a low-profile place to hide and entered the town of Theog.

Shanmugham and his crew plan to conduct minor robberies to get enough funds to sustain themselves. They rob highway users at night, but the gang member (Sandy) is out of control and shoots one person who was travelling alone in his car. Shanmugham is not happy with this gang member but is unable to control him either.

Parthi tries to appease them by giving them money, but one of the gang members (the same guy who sexually assaulted the little girl previously) makes a move on his employee Shruthi (Janany Kunaseelan). Enraged, Parthi beats up all of them. Shanmugham takes Shruthi hostage and asks his gang member to kill Parthi. But the gang member attempts to kill Chintu instead. Parthi snaps and guns all of them down without hesitation, but later has an emotional breakdown.

Initially arrested, Parthi is released for having committed the murders in self-defense, but his photograph appears in newspapers all over India. One such image is seen by Harold Das (Arjun Sarja), a gangster in Telangana, who informs his elder brother, Antony Das (Sanjay Dutt) about him. Antony immediately leaves with his men for Theog. Anthony says that if Parthi is really Leo, then even 400 men would not be enough to stop him.

Meanwhile, Shanmugham's relatives attempt to kill Parthi and his family in a crowded market in Theog. Parthi again brutally repels the attack resulting in the death of Shanmugham's relatives. Only one man, who was Shanmugham's brother-in-law (Madhusudhan Rao), manages to escape. This prompts him to request a high-ranking, armed police officer from Tamil Nadu to be sent to his house for protection. Police Officer Bhawar Jetha (Mukhtar Khan) insults Parthi for asking for an armed guard outside his house and insults his wife as well. This again triggers Parthi and he grabs Bhawar by the throat and almost kills him. Parthi then asks Joshy to deliberately slash his back to show that he has been badly injured in the various attacks, to justify police protection in front of a judge.

Parthi's request is granted as Napoleon (George Maryan), having been promoted following his heroics in Tiruchirappalli, is assigned to protect his family. Napoleon is a short and stubby man, who is asleep most of his time on duty. Parthi knows war is coming and spend his time forging all sorts of fatal weapons and bear traps.

On meeting Parthi, Antony insists that Parthi is his son, Leo Das (born on 13th May 1977) who was presumed to be dead, but Parthi vehemently denies this. Antony threatens him to accept his identity and surrender or face the consequences. The next day, Sathya and Chinku go shopping and are attacked by Shanmugham's brother-in-law and his henchmen. Parthi was at the cafe, but this time Antony steps up to defend the family and brutally kills the attackers.

Antony meets Sathya and tells her that Leo is a mass murderer, prompting her to dig into Parthi's past. At the same time, Joshy starts digging into Leo's past and learns about his friend, Hridayaraj D'Souza (Mansoor Ali Khan), who was arrested and is to be hanged in three days. Joshy meets with Hridayaraj, who narrates Leo's alleged past.

In 1999, Antony established a tobacco factory called Das & Co. Harold returned to India from Canada and started manufacturing and smuggling a drug named Datura (which is considered more dangerous that cocaine), using the factory as a front as their tobacco products did not take off. Antony was a devout Christian and sacrificed an animal before starting any new business. But later, he started sacrificing humans as well. Antony's twin children, Leo and Elisa Das (Madonna Sebastian) who were both 20 years old at the time, did the dirty work for them to run the business smoothly. Leo managed the drug operations and oversaw their transfer across state and international borders. Being a strong believer in the occult, Antony tried to sacrifice Elisa based on his astrologer's advice, as this would have allowed their tobacco products to take off. Leo did not believe in Antony's superstitions and asks him to release Elisa. Elisa tells Leo not to beg for her life and asks him to kill everybody instead. Enraged, Leo set fire to all of Harold's drugs (the fire destroyed the tobacco factory and killed 43 men), but Harold managed to kill Elisa and Antony shot Leo, who was since presumed dead.

After listening to Hridayaraj, Joshy is convinced that Parthi is not Leo, while Sathya also gets definitive proof of the same. Meanwhile, Antony kidnaps Siddhu and tells him that he will sacrifice Siddhu as he could not sacrifice Elisa with his own hands.

Parthi and Napoleon give chase to Antony and his men, and Parthi eventually catches up with them. He finishes off Antony and his men but does not find Siddhu. Harold learns about Antony's death and calls Parthi to bring Antony's body in return for Siddhu. As Parthi goes to Harold's lair, Harold reveals that he has sent men to kill Sathya and Chintu.

Harold's men attack Parthi's family at their house, but Parthi had set up defenses in the form of traps and IEDs and manages to fend them off. Joshy and Napoleon kill the ones who manage to make it their front door. The last man standing reaches Sathya and Chinku, but that when the hyena emerges and rips the attackers to pieces.

As Harold and Parthi engage in a fistfight, Parthi grabs a gun and holds Harold at gunpoint. At this point, Harold gets convinced that Parthi is not Leo and states that he and his family can walk away freely. However, Parthi starts laughing and finally admits he is Leo before gunning down Harold, rescuing Siddhu and torching the entire Das & Co. factory. Parthi states that he has done nothing good as Leo and anyone who insists on knowing his true identity must either die or already be dead. A flashback reveals he admitted his true identity to Antony before killing him.

In an epilogue, as peace returns to Parthi's life, he gets a phone call. The caller reveals that he knows Parthi is Leo and tells him that destroying only his family's Datura factory was not enough to make the society drug-free as drugs are rampant all over India. The caller also says that he knows Parthi recognizes his identity, as Parthi sighs in exasperation.