Plot
Parthiban "Parthi" is an outwardly humble wildlife rescuer and café proprietor living with his wife Sathya, son Siddharth "Siddhu" and daughter Mathi "Chintu" in Theog, Himachal Pradesh. One day, his forest ranger friend Joshy Andrews seeks his help in taming a spotted hyena creating chaos; Parthi tames the hyena with the help of Siddhu and adopts it subsequently, but chooses to avoid media coverage. Meanwhile, a group of merciless burglars headed by Shanmugham threaten the townsfolk and intrude Parthi's café at its closing time. When they intimidate Parthi with the lives of Chintu and his employee Shruthi, he shoots them dead. Parthi is arrested, but acquitted after the killings are concluded to be in self-defense.
After surviving an assassination attempt by Shanmugham's brother-in-law, Parthi appeals for a Tamil-speaking police officer to protect him and his family. Napoleon, who has been promoted due to his heroics in Tiruchirappalli, is assigned that position. Meanwhile, owing to the incident, Parthi's photographs appear in newspapers nationwide and draw the attention of Telangana-based drug baron brothers Harold and Antony Das. Antony promptly leaves for Theog, having recognised Parthi to be his thought-to-be-dead son Leo; Parthi, nevertheless, fiercely denies his claims. Disbelieving Parthi, Antony meets Sathya and tells her that Parthi is his son Leo, an infamous criminal. Suspicious, Sathya and Joshy separately investigate Parthi's past. While Sathya meets Parthi's childhood friend, Joshy meets Leo's friend Hridayaraj D'Souza, a soon-to-be-executed convict, who narrates Leo's alleged past.
In 1999, after Harold returns to India upon completing his education in Canada, he begins manufacturing and selling a stimulant drug named Datura, using Antony's failing tobacco factory Das & Co as a front organization. Antony's twin children Leo and Elisa assist the brothers in their activities. Antony is also a staunch believer of occult practices and engages in human sacrifices to succour their business. During a celebration, Antony is told by an occult priest that sacrificing one of his children will grant him enormous success; he chooses Elisa and urges Leo to cooperate, but he strongly resists and fights Antony and Harold. In the process, he sets the drugs on fire but fails to protect Elisa from getting killed by Harold. She pleads with him to abandon the business and lead a peaceful life, before dying. Leo is then shot by Antony and is presumed dead since.
On hearing this, Joshy is convinced that Parthi is not Leo, while Sathya is also convinced the same. Parthi discerns that Sathya is suspecting his identity and confronts her but they eventually reconcile. Antony informs Parthi that he has kidnapped Siddhu and that he is going to be sacrificed. Parthi and Napoleon give chase to Antony and his men; Parthi successfully subdues them and kills Antony but does not find Siddhu, who is revealed to have been held captive by Harold at Das & Co.
After Harold agrees to return Siddhu in exchange for Antony's corpse, Parthi takes the latter alone to Das & Co, but realises that Harold has double-crossed him by sending henchmen to murder Sathya and Chintu. While Joshy, Napoleon and the hyena protect Sathya and Chintu by killing the henchmen, Parthi fights Harold and subsequently holds him at gunpoint. Harold finally agrees that Parthi is not Leo and assures no harm to him and his family. However, Parthi laughs loudly and confirms he is Leo before shooting Harold dead and rescuing Siddhu. While torching Das & Co, Parthi asserts that he has done nothing good as Leo, and that anyone who knows his identity must die or already be dead, recalling that he admitted the truth to Antony before killing him.
While back in Theog, Parthi receives a phone call. The anonymous caller tells him that he knows he is Leo and contends that destroying his family's factory will not make society drug-free, imploring him to join his mission and correctly surmises that Parthi might have recognised him by now, following which he sighs in exasperation.
