context: On the night of 11 October 1943, the Japanese bombed the Indian city of Madras (now known as Chennai), causing commotion all over the city. In Triplicane the next morning, Rajan (Sivaji Ganesan), a radio engineer and communications researcher, is found murdered with his own hand gun. His neighbor Chinnaiah Pillai (P. D. Sambandam) hears the gunshot and complains to the police. A local Police Inspector named Purushothaman Naidu arrives and investigates the scene. He is joined by C.I.D. officer Sivanandam (Javar Seetharaman)there. He concludes that the killer is some petty thief who must have shot Rajan for the lump of money found in the same room of the crime scene. However, Sivanandam states that to be of a bad solution, as the amount of money matches exactly with the withdrawal entry in the bank passbook found in the same room, without a single rupee's difference. Nonetheless, it was clear Rajan was making plans to leave Chennai, in anticipation of the bombings. Rajan's wife Usha (Pandari Bai) is almost dumbstruck and unable to speak during any inquiries. Sivanandam and Naidu feel reluctant and embarrassed to do any questioning to her.The two decide to investigate the case by questioning the people in and around the house, who are the family members or friends of Rajan. They first do their inquiry with Chinnaiah Pillai, the neighbour as he is the first to inform them. He tells that the killer could probably be Pattabi, Rajan's younger brother (T. K. Balachandran). He recounts an incident (as flashback), in which Pattabi confronts Rajan at the house's garage to ask for his share of the family property to be apportioned and given to him. Rajan, in good faith, denies to give Pattabi his share, feeling that he and his wife might squander it. Chinnaiah concludes that this would have kindled Pattabi to kill Rajan.Sivanandam and Naidu decide to inquire Pattabi. However, Pattabi had rushed to the Beach before their arrival, probably to commit suicide. They rush there themselves to inquire him. When questioned, Pattabi feels remorseful of his brother's death. He states that he did treat his brother well when he was alive and did not understand his good intentions. He recounts another incident where his wife Hema, had fought with him herself, during dinner for the apportionment of property herself. She is also a person who loses sanity when overpowered by anger. Pattabi believes of a very good possibility, that Hema used the Rajan's gun to shoot him for the money.Sivanamdam parts to meet Hema soon after, to do his inquiry. Hema was initially impudent and refusing to give her statement of the crime, but later gives in when threatened to be arrested for the same. She reveals a secret of Rajan. Rajan has had extramarital affair with a dancer named Ambujam. She knew this when she once found and overheard Rajan and Ambujam speaking together a week before the murder, where Ambujam unveils that she is pregnant. Rajan treats the news with a reckless attitude, infuriating Ambujam. Hema had received a letter addressed to Rajan from Ambujam, that had the address "No.15, Thoni Street". Hema proposes that Ambujam could have killed Rajan in retaliation to Rajan's lack of concern for her.Fatigued with the case's complicated nature, Naidu compares it with a supposed "Peruvala Vaikal" in Trichy, a river that has a lot of twists and turns. Sivanandam makes a better analogy of the case, to the story of "blind men and an elephant", where each suspect has a different and contrasting opinion to offer. In Thoni Street, Ambujam has made preparations to leave Chennai, at the news of Rajan's death. Half-an-hour after her departure Sivanandam and Naidu arrive there to find the house locked. They take with them Shanmugam, a boy in the street to the Police Station to inquire him on the physical features of Ambujam, to locate and recognize her. The boy knows and has seen her leave from Thoni Street. In a coincidence, Ambujam's bullock-cart and another car strike each other in a road accident, right in front of the very same police station. They identify and inquire Ambujam.Ambujam accuses Chinnaiah (Rajan's neighbour whom they had inquired as the very first suspect) of the murder. She explains that Chinnaiah was her foster father, who wanted her to stay away from Rajan. She started loving after the trio's meeting on a picnic. When their relationship started deepening, Chinnaiah got infuriated and wanted put an end to the affair. Ambujam gives a strong opinion that it must have been Chinnaiah who killed Rajan.Sivanandam does his homework by developing the film roll found in Rajan's camera, collecting and comparing all of the suspects' and others' fingerprints with those found in Rajan's shoes, finding a teardrop mark in Rajan's shoes and finding broken bangle pieces on the crime scene. He finds them further complicating the case and coming nowhere near the conclusion. He gets small clue at a sharbat shop, apparently making no sense. He make inquiries to Rajan's college (Victoria College) principal Ranganathan, who has a high opinion of both Rajan and Usha, his wife, both being his alumni. He says Rajan once broke into the college at night, to complete an experiment, for which he never felt guilty and also Usha once put up the Indian flag as part of Freedom Movement and she accepted doing it herself. This emphasizes her patriotism.Sivanandam inquires finally, Usha. She narrates an incident during college where Rajan spoke of individualistic needs that are equally as important as the country's freedom. He managed to convince the entire crowd of his viewpoint, who previously opined the opposite. However, he was bullied and disdained when Usha took over and changed the crowd back to "giving your life for the nation". Usha further tells Sivanandam on how she and Rajan came to love each other. In the process, he tricks into collecting Usha's fingerprints with a leaky fountain pen.On that eve, Sivanandam meets all the suspects along with Naidu at Rajan's residence. He caries our an exercise wherein the suspects including Usha must shoot Sivanandam, assuming that he is Rajan. They are given revolver's with false bullets. Usha is unable to shoot. Then Sivanandam orders an (apparent) arrest of Pattabi and Hema. Unable to bear the torture, Usha comes out with the truth. On the day of the murder when she entered the room she found Rajan working with something meticulously, with a radio equipment, powered by a generator. She doubts of something suspicious. The second time she enters she discovers that he is part of the terrorist activity of bombing Chennai, communicating to the Japanese bombers. He is a key part, of the bombing. Out of her extreme patriotism for her nation, and unable to bear the injustice she tries to talk and mend Rajan's ways. However, Rajan feeling that he should help the Japanese (who helped him with his Radio business), and does not mind betraying his own country. Usha attempts to shoot Rajan whose plan is to escape to Japan in a submarine after the bombing, for which he had packed the money. However, in an accident, fighting for the gun, the trigger is accidentally pressed killing Rajan. She has cried at his boots later, holding them, explaining the fingerprints and teardrop stain.Sivanandam and Naidu ask for the papers Rajan used to hatch the bombing plan. She goes inside to fetch them. Sivanandam tells Naidu that the fingerprints on the boots and hers which he collected, matched, which led him to suspect her. Also, her failure to shoot during the exercise confirms the fact. When Usha takes a long time to come back, the two hear a long silence followed by a gunshot and run inside. Sivanandam shouts "Usha!" followed by a screen closing behind them.
question: Who did Rajan want to sell radios to?
answer: Japanese