Set in rural Bengal, Antariksha revolves around the family of an authoritarian zamindar. Raised by the family, a young man Jayanta handles their accounts. Jayanta is in love with his childhood sweetheart Bani, the daughter of a priest. On the day of Dol (Holi), Jayanta secretly marries Bani. When her father finds out, he discloses a secret to Jayanta that he must guard with his life.
The zamindar’s wife, who loves Jayanta as her own, tells the zamindar to arrange a proper wedding ceremony for him. Following the wedding, the two lead a blissful life and soon, Bani is pregnant. Jayanta travels to Kashi, and the priest asks him to deliver a letter to a man named Kalipada. When he has delivered it, Kalipada hands him a letter as well, which is stolen by some thieves. Dismissing this, Jayanta comes back home.
The newlywed couple’s happiness is disrupted when a mysterious relative of Bani’s turns up at their doorstep. Claiming that his name is Gagan Ganguly, he tells them that he has a letter that could threaten Bani’s survival, and uses this to extort money from Jayanta. Independent and upright, Jayanta attempts to put together some funds without anyone’s help. When he cannot, he decides to run away with Bani. Unfortunately, Gagan intercepts them, and threatens Jayanta with a knife. A fight ensues, and Jayanta ends up killing Gagan. Bani is hurt in the struggle as well. Jayanta is arrested, but the zamindar decides to leave him to his fate. Meanwhile, Bani goes into labour, and the zamindar’s wife rushes to help. The priest finally reveals the secret he had disclosed to Jayanta, and he reminds the zamindar of his duty towards others. When Bani gives birth to a son, the zamindar’s stern resolve is broken, and he hastens to the police station to free Jayanta.