Aalavandhar M. R. Radha is a prosperous jeweller who shares his life with his wife Maragatham M. V. Rajamma and their two sons, Rajan Gemini Ganesan and Ramu Sivaji Ganesan. Driven by greed, he murders a fellow jeweller who comes to sell him diamonds and, to dodge suspicion, cleverly pins the crime on his worker, Manickam Pillai T. S. Balaiah. The impact of the crime ripples through the entire household: Manickam Pillai’s wife dies of shock after giving birth to a daughter, and a sympathetic neighbour leaves the baby in Maragatham’s care while taking the elder daughter away. Maragatham then entrusts the infant to their family friend James S. V. Subbaiah.
On learning of his wife’s death—and before Aalavandhar can be arrested—Manickam abducts Ramu on the way to prison, intending vengeance. A local Muslim doctor Chittoor V. Nagayya intervenes, saves the child, and raises him in his own home as Raheem. Thus, four children grow up in separate worlds: Rajan with Aalavandhar, Raheem with the doctor, Thangam Savitri with the neighbour, and Mary Devika with James. As adults, Rajan and Thangam fall in love, while Raheem and Mary also share a deep, mutual affection, each pairing protected by the circles they inhabit.
Aalavandhar’s illegal schemes continue unabated. Raheem, now working in the doctor’s household, becomes a champion for the rights of people living in a nearby slum—one that Aalavandhar claims as his own property and intends to sell for personal gain. The moral conflict intensifies as Aalavandhar schemes to marry Mary to Rajan to seize James’ property. When Raheem’s love for Mary becomes known, Aalavandhar strikes back by pouring acid on Raheem while he sleeps; the assault leaves him disfigured, yet Mary’s devotion endures.
In a calculated move, Aalavandhar brands Raheem as a thief and an attempted murderer, sending Raheem to prison. During this time, the slum is cleared, and Manickam—now released after good behavior—returns as James’s driver, hoping to be near Mary. Rajan, who has become a police officer, discovers his father’s wrongdoing and, after a tense confrontation, resigns from the force rather than stand by and do nothing against Aalavandhar. Raheem is released on bail and plans to marry Rajan and Thangam, but Aalavandhar’s rage leads him to trap Raheem in a hut and set it on fire.
The truth finally comes to light when Manickam reveals to Maragatham that Raheem is her son Ramu, the child he had kidnapped years earlier. United by this revelation, the family races to rescue Raheem. Aalavandhar, confronted with the full consequences of his actions, experiences a moral awakening, saves Raheem, and surrenders to the police. In the end, the clan reunites and commits to living in harmony across religious divides, a quiet testament to forgiveness and unity.
