Bairavaa, a tough collection agent for ICCI Bank in Chennai, is willing to push hard—甚至 using violent means—to recover money from debtors. At his manager’s daughter’s wedding, he spots Malarvizhi Keerthy Suresh, a medical student from Kallidaikurichi in Tirunelveli district, and finds himself drawn to her. He pepperks her with charming, hopeful talk as he tries to get to know her better. When he heads to the Koyambedu bus station to propose before she leaves Chennai, he spots her surrounded by thugs who plan to kill her for alleged involvement in an attack on the Union Minister’s son Charan [Roshan Basheer]. The danger subsides only after Periyakannu alias PK [Jagapati Babu] speaks up and orders the men to back off. Bairavaa confronts Malar, who explains why PK spared her life and the web of power that protects him.
Past deeds unfold: Malar studies at PK Medical College in Tirunelveli, where PK, a butcher-turned-influential gangster and politician, sits at the helm with his loyal right-hand man, Kottai Veeran [Daniel Balaji]. The college is run-down, lacking basic facilities, doctors, and a proper building. When the Medical Council of India (MCI) considers suspending the college for these failures, PK barters a shady deal to save face: the officials will sleep with a girl from the college. Vaishali [Aparna Vinod] is chosen and is later found raped and dead. Malar’s police officer father is murdered by PK in retaliation as the investigation digs deeper into PK’s involvement. In the wake of her father’s death, Malar files a petition against PK in court; a judge rules that she cannot be expelled and must be protected until the case resolves. PK respects the judge’s decision but begins to pressure Malar through the college staff, even cutting off power and water to intimidate her. He plans to finish her off once the verdict favors him. During the wedding, Malar hands over the video evidence of Vaishali’s assault to Charan, who can access NIC to probe the footage. PK’s henchmen attack Charan, who seizes the video and tries to pin the blame on Malar.
Present tense action: Hearing Malar’s story, Bairavaa vows to help her fight PK and seek justice for Vaishali. He defeats the goons at the wedding and travels to Kallidaikurichi with Malar. Posing as an income tax officer, he conducts a raid at PK’s mansion and seizes crucial evidence linking PK to Vaishali’s death and the college’s corruption. PK races back to Malar’s home to retrieve what he thinks is the proof, but Bairavaa refuses to surrender it. With no proof in hand, PK backs off for the moment, taunting the hero as he slips away. Bairavaa faces a new setback when PK’s associates abduct him and bring him to Kottai Veeran’s lair, but the hero fights his way out amid a tense melee.
PK realises he’s on the back foot only when he regains the incriminating documents and destroys them, forcing a new five-day window for Bairavaa to gather fresh evidence. A further attack follows: PK’s goons attempt to burn Bairavaa alive and orchestrate a petrol-bunk murder, but the protagonist survives. The danger escalates when Malar’s sister’s daughter is kidnapped; Bairavaa rescues her, sustaining gunfire and a metal rod injury in the process. He’s seized again by Kottai Veeran’s men but escapes. A turning point arrives when Bairavaa discovers Kottai Veeran’s wife has died. He exploits PK’s obsession with his late wife, convincing Kottai Veeran to switch sides and become an approver against PK.
In a crucial gambit, Bairavaa swaps PK’s asthma inhaler with nitrous oxide. PK, unaware of the switch, inhales the gas at a funeral and bursts into uncontrollable laughter, undermining PK’s power and turning Kottai Veeran against him. The betrayal blooms into PK’s downfall as Kottai Veeran edges toward alignment with Bairavaa. After PK betrays him, Kottai Veeran is hacked, and Bairavaa leads a final raid to confront PK’s goons in an abandoned building. He fights through the danger and narrowly escapes the same fate that claimed Kottai Veeran.
With PK cornered, Bairavaa constructs a bold frame: PK is accused of plotting to assassinate the Prime Minister while en route to the Kudankulam Nuclear Power Plant. The national media frenzy forces the government to order PK to be shot on sight. Cornered by real NSG commandos, PK attempts to kill Bairavaa in a brutal last-ditch assault, but the hero subdues him and escapes, disguising himself as an NSG operative to blend in with the mounting assault. In the end, the court rules in favor of Bairavaa and Malar, and PK Medical College’s students are moved to another institution. In a public press conference, Bairavaa emphasizes the importance of education and urges private colleges to provide basic facilities for students. The couple, Bairavaa and Malar, marry and begin a new life, while Vaishali’s last rites are performed by the family to honour her memory.
