Aalavandhan
Vijay Kumar, a Commando in Delhi is due to marry his girlfriend Tejaswini "Teju", a television news presenter. Vijay's twin brother Nandu is a psychopath with schizophrenia. They both were separated as children and Nandu spent most of his life in an asylum for killing his stepmother. Vijay cares about Nandu and looks forward to his release, but a doctor tells him that Nandu is a danger to the society and should not be released.
Vijay and Teju visit Nandu to share the news about their impending marriage, which turns disastrous when Nandu sees in Teju his stepmother Jayanthi, who he hates for ruining his life. Seeking to save Vijay from Teju, who he sees as the "witch", Nandu manages to escape custody after killing two other inmates. Nandu later meets his maternal uncle—responsible for admitting him in the asylum—who dies on seeing him. After their marriage, Vijay and Teju are shocked on learning of Nandu's escape. The doctor believes it was another patient who escaped, but Vijay is convinced that it was Nandu.
Nandu visit's Vijay's home when he is not there and leaves a message to kill Teju. He keeps conversing with his deceased mother in his imagination. While searching for Teju, Nandu meets singer Sharmilee and both develop a liking for each other. Soon, Nandu gets hallucinations where he sees Sharmilee as his stepmother and brutally murders her. Regretting his actions, he burns her corpse before exiting the room, but leaves behind evidence through which Vijay deduces him as the murderer.
Vijay and Teju leave for Vijay's ancestral home in Ooty to stay safe from Nandu, but he secretly follows them. Vijay and Teju find Nandu's old diary in the house through which they read his past: Vijay and Nandu's mother committed suicide due to their father Santosh's affair with Jayanthi, who later became their stepmother. Both brothers hate her and Nandu becomes violent at school. The teacher complains about it and Nandu justifies that he is only reflecting the home environment. An enraged Santosh beats both his sons for abusing his wife. One day, the brothers see Jayanthi having an affair with another person and Nandu tries telling this to his father who pays no heed, and instead beats him. Nandu pleads to his maternal uncle to take him along with him. But as he is suffering from throat cancer, he refuses and suggests a boarding school. Eventually, Vijay leaves with his uncle to a boarding school while Nandu remains home.
The situation gets worse at home with Nandu and Jayanthi turning violent and Santosh gets a heart attack. Nandu overhears a conversation between his stepmother and a lawyer, and realises that she is after his father's wealth. Seeing this, Santosh dies due to another heart attack. Nandu is now shocked to see both his deceased parents in his hallucination. His mother gives him the mission of killing Jayanthi, which Nandu does. Nandu stays with the corpses in the house before being incarcerated at the asylum.
In the present, Vijay learns from his old friend Thenkoshut that Nandu has reached Ooty. Vijay reaches on time to save Teju from Nandu, who entered their hotel room and leaves with her. Nandu chases the car in which they escape. After a long chase, Vijay manages to push Nandu's car into an abyss and assumes he is dead. However, Nandu escapes and continues his trail. Vijay plans to leave the city and notices Nandu coming to the hotel secretly.
Vijay and his commandos try to nab him but he takes on everyone. He even finds and corners Teju who starts whacking him with a belt in self-defence, mirroring Jayanthi's manner of punishing Nandu, convincing him that Teju is indeed Jayanthi's reincarnation. Vijay reaches by then and there is a fight between the brothers, in which Nandu overpowers Vijay. Suddenly, Nandu sees his mother asking him to join her as Jayanthi is torturing her up there. He realises his mistake and apologises to Vijay for chasing Teju. To kill his stepmother, he lights up some cylinders despite Vijay's request not to do so and to return. The cylinders explode and kill Nandu.
good versus evil, psychedelic, murder, violence