Mandhira Punnagai (Tamil: மந்திர புன்னகை),(English: Mystic Smile) is a 2010 Indian Tamil-language psychological thriller-drama film written and directed by Karu Pazhaniappan, starring himself in the lead role, along with Meenakshi and Santhanam. The film was released on 19 November 2010.
The film tells the story of an architect, Kathir (Karu Pazhaniappan), who is talented but also forthright in his dealings whether in office or in his personal life. He doesn't have any girlfriend or many friends whether at work or in personal life.
When he is asked to design a spanking new showroom for Honda Dealership, Nandini (Meenakshi) one of the employees there meets Kathir in connection with the new design and falls in love with Kathir's forthrightness unbeknownst to him. He doesn't pay much attention to Meenakshi's overtures initially, perhaps influenced by his troubled childhood.
He is approached by Shankar (Rishi), Nandini's colleague who happens to like her, to find out what it is that attracts her to Kathir, for which Kathir drags Shankar to Nandini's house and asks him to convey his love for Nandini himself. This increases Nandini's attraction towards Kathir's straightforward attitude. Gradually, Kathir starts to like her but at the same time he also fears that she is cheating on him and tries to kill her.
He goes to the police station confessing his crime that he killed her. When police come to find the body in his apartment, they are unable to find the body. Kathir's friend Manmadha Naidu (Thambi ramaiah) says that last night Kathir was talking to himself and broken all the things in a fit of anger (When Kathir saw Nandini sleeping with Srikanth, Kathir got angry broken all the things imagining himself as killing Nandhini).
Kathir had a troubled childhood where his mother eloped after her illegal affair with his father's friend came to light and his father committed suicide after finding out about the affair at the same time, which made him to view things in a different light. In the end, Nandini claimed that she planned things to make him reform him but Kathir in anger says that he celebrate people dying.
In next scene, kathir receives a call that nandini had committed suicide he immediately goes to hospital and finds out that nandini didn't commit suicide and she gave him shock to make him realize the wrongdoings. The film ends with Nandini and Kathir uniting, reflection of kathir's father gives acceptance.