Anniyan is the story of Ramanujam "Ambi" Iyengar (Vikram), a lawyer who suffers from Multiple Personality Disorder
. Ambi is an innocent and honest lawyer . If he comes across anyone not obeying the rules he files cases against them but all his efforts go in vain
. His constant habit to be perfect in rules and honesty leads him to develop a Multiple Personality Disorder in which a new character in him grows as Anniyan (Vikram) and starts a website calledto hear people's complaints . The new character, Anniyan , is a violent man. When he is Ambi and comes across a person who does not obey rules he makes complaints in his website  . When he is Anniyan, he goes and kills them by methods used for torturing people in hell. He apparently takes the definition of these methods from the Garuda Purana
.