Guna (Kamal Haasan) is a mentally affected person and receives treatment in a mental hospital in Hyderabad. He does not like his father, and his mother Manonmani (S. Varalakshmi) is a moll in the house that they live. He assumes a fictitious character named Abirami (also the name of an Indian goddess) and registers in his mind that she is an angel who is going to marry him on a “full moon day”. After coming out of the asylum, he believes the story to be true and believes that his Abirami is somewhere around.
A bunch of hooligans led by Guna’s uncle (Janagaraj) trick Guna into robbing a temple of Abirami, an Indian goddess. He happens to see a rich girl (Roshini) in there, right after his uncle tells him that “Abirami will come”. He decides that she is the one, and in the confusion following the robbery, he takes her with him to a lonely, damaged house situated at the top of a hill in Kodaikanal. Police start investigation regarding the robbery and missing of Roshini. Initially, Roshini hates him for his weird nature and for holding her captive.

Bala (Gemini Ganesan) and Bhanu (Jayanthi) are a happily married couple. Everything seems fine till Sheela (Vanisri) enters their lives. Bala is a tennis champion and Sheela claims to be his fan. The family members raise objection to this liaison but Bhanu trusts her husband blindly. Bala takes undue advantage of this trust and continues to meet Sheela on the sly till one day Bhanu stumbles upon the truth. This breach of trust breaks Bhanu which eventually leads to her death. An unrepentant Bala takes this as an opportunity and proposes to marry Sheela. His mother is shattered but gives in to his demands. An elated Bala rushes to Sheela only to find her missing! Was it poetic justice?

Emperor Raja Raja Chozan seems to count a little too much on his newly-appointed, deceptive minister. But he knows what he is doing.