Pattakathi Bairavan (Sivaji Ganesan) is a notorious criminal sought by the police for several murders which he commits using his customary dagger (pattakathi). When in jail, he encounters his adopted father and after an escapade he murders his boss Dharmalingam (R. S. Manohar), who had ruined his adopted family. He also reunites with his step-sister Deepa (Sridevi) and camouflages himself as Karnan, a rich businessman to deceive the Police. Deepa's close friend (Jayasudha) is Bhairavan's romantic interest, but in a twist, Deepa herself is in love with Police officer Arjunan (Jai Ganesh), who is actually on a mission to find and eliminate the elusive Pattakkathi Bhairavan. Bhairavan approaches Arjunan quite convincingly masquerading as businessman Karnan, but Arjunan's mother (Sowcar Janaki) realizes Pattakkathi Bhairavan a.k.a. Karnan is none other than her own first son whom she had borne out of wedlock, but struggles to tell him the truth, since he professes a profound hatred for his unknown mother, who he believes had dumped him in a garbage bin as a baby. How the events unfold form the rest of the story.
