The film starts with the young woman Panchali getting off the train named 'Kizhakke Pogum Rail' and lands in the village Thamaraikulam which follows strict rules. There, Panchali is accommodated by her sister Karuthamma and her brother-in-law Ramaiah, Panchali informs her that their mother died a couple of days ago. Ramaiah starts to have an eye on Panchali. Paranjothi is an unemployed graduate and a big fan of the poet Subramania Bharati who lives his father Maruthu and his sister Kanniyamma. His father Maruthu is a barber and considers Paranjothi as a good-for-nothing like all the villagers. After getting married, Kanniyamma leaves her birth home to live with her husband's family. Panchali and Paranjothi slowly fall in love with each other. One day, the villagers spot Paranjothi running behind Panchali. At the gram panchayat, the panchayat members blame Paranjothi for trying to misbehave toward the young woman. Only the retired military man Pattalathaar and the farmer Ponnandi support him, but the panchayat members overlook them, and they punish him. Maruthu shaved off the hair of his son and Paranjothi parades on a donkey in the streets of the village whereas Ramaiah forces his wife Karuthamma to burn Panchali's arm with a piece of wood. After the humiliation, Maruthu commits suicide in the village's lake, Paranjothi decides to leave the town, and he promises Panchali that he will come back to marry her. He also informs her that he will write a message on the last compartment of the 'Kizhakke Pogum Rail' train. In the city, after several interviews, he finally finds a decent job. In the meantime, at the village court, Ramaiah complains that Karuthamma is a barren woman and he expresses his wish to marry Panchali. A few days later, the village is battered by heavy rains. To stop the rain, the villagers contrive the way to stop it, executing an ancient belief: one virgin woman has to walk naked around the village at sunrise. Unexpectedly, Panchali is chosen to be that woman. The day of the ritual, Paranjothi gladly returns at his village, and he sees Panchali completely naked. Even though Paranjothi was devastated, he covers Panchali with his Dhoti and they both run away from the angry villagers. Pattalathaar helps the couple by stalling the villagers, and he is killed in the process. The lovers manage to catch the running train 'Kizhakke Pogum Rail' under the eyes of the villagers.
Kizhakke Pogum Rail was Raadhika's debut film. She contemplated leaving the film throughout the shoot, but was "offered chocolates" to complete the film. It was also the Tamil debut for Vijayan. The producer offered K. Bhagyaraj to direct, but he declined as he wanted to "complete at least a couple of more films as an assistant". Bhagyaraj remained as an assistant director.
Kizhakke Pogum Rail was a major commercial success completing 365-day run at the box office, and Raadhika became popularly known by the sobriquet "Rayil Radhika".
