Anniyan is about Ramanujam alias Ambi who suffers from Multiple Personality Disorder. Ambi (a lawyer), Remo(a suave supermodel) and Anniyan (a vigilante who wreaks havoc on people who cheat, loots or conned Ambi).
Raghavan is an ex-convict who is redeeming his life after his release from prison. He stumbles upon Anjali, a journalist who decides to write an autobiography on his life. The story progresses as Raghavan discloses his past.