The story of the film revolves around the concept of Ifrit, the son of Satan and Auladhchakra, a satanic cult in Bangladesh aiming to propagate and progress the bloodline of Ifrit. They seared the women impregnated by Ifrit with the symbol of a foetus on their skin. Rukhsana (Anushka Sharma), is the daughter of a woman who was a victim of a sex ritual by Auladhchakra. She is afraid of incense sticks and religious hymns and prayers, and hides her head in a bucket of water to cut out the Azaan playing in a nearby mosque. Professor Quasim Ali (Rajat Kapoor) used to head a group of vigilantes which sought out women impregnated by Ifrit, and killed their babies by chopping off their heads. This drew a lot of flak from villagers and the group was ultimately shut down due to its radical approach.
The film begins with Arnab (Parambrata Chatterjee) meeting Piyali (Ritabhari Chakraborty) on the roof of her house. Arnab has come to meet her for marriage arranged by his family. Piyali is a nurse, while Arnab runs a printing press. While returning from her house, in the heavy rain, with his father driving, they hit an old woman. Although the woman died by being run over, Arnab files the case with the local police inspector (Santilal Mukherjee) as attempt to suicide. On visiting the accident spot, they discover the place where the old woman used to live, locally called kuttewali budhiya, meaning dog lady, in a hut in the forest by the road. Rukhsana is found chained in a dark corner of the hut, pale and bruised. Arnab takes pity and after taking Rukhsana to visit her dead mother, he decides to take her in later in the film.
Meanwhile, a mortuary assistant (Dibyendu Bhattacharya) who made a living stealing golden teeth and the likes from corpses in the morgue, and who initially worked with the professor, discovers that the dead woman, Rukhsana’s mother, has the mark of foetus on her skin. He decides to inform the professor and they decide to seek out Rukhsana. They reach Rukhsana’s hut in the forest, only to find that she had escaped. Later they track down Rukhsana to Arnab’s house, where she was supposed to stay until he found housing for her.
Rukhsana seemed to be abused since her childhood. Arnab observes that she doesn’t have a soul to care for her, and hence takes care of her. Rukhsana inadvertently falls in love with him, but also has hallucinations of herself bleeding when she is alone. The professor meets another old woman, supposedly born of Ifrit, a kalapori(Mansi Multani), who seemingly can communicate with others like her. She tells him where Rukhsana is, and that she is going to seduce the guy she is living with to pass on the bloodline.
One night, Rukhsana gets the urge to drink blood and kills a dog near Arnab’s house in the middle of the night. The professor ultimately approaches Arnab and tells him her story, but he refuses to believe him. One evening, the morgue assistant follows Arnab, and they end up in a scuffle, leaving Arnab bleeding. Rukhsana tends to him and tells him of her affection for him. She also kills the morgue assistant who had hit Arnab. She finally succeeds in getting impregnated by him, but then her attitude changes. She forces him to stop meeting Piyali, whom she sees as competition. On further argument, she grabs him by his throat and lifts him clear off the ground. This brings him to contact the professor and find out more about Ifrit.
The Ifrit cannot be seen but only heard by its breath. Ifrit babies can be born by latching on to human wombs. The babies are born over a month instead of nine months, and without an umbilical cord. So when Rukhsana tells Arnab that she is pregnant, he contacts the professor to take care of it. Piyali had come by his house once, and finding Rukhsana in his room accidentally, breaks all contact with him. So, while the professor tortures Rukhsana so that her anger poisons her body, Arnab withdraws himself from his normal life and society, and stays at his parents’ home.
After one month, Piyali comes over to tell Arnab that he must convince his parents that she isn’t the reason for his voluntary loneliness, but instead gets to hear the truth about Rukhsana. She also confesses about an earlier relationship and an aborted baby of her former boyfriend. But things soon take a turn for the worse.
On the last day of the month, Rukhsana sets herself free. She is seen killing the professor before heading over to Piyali’s house. Arnab heads over to his own house to find the others dead, and hurries over to Piyali’s house. Rukhsana manages to injure Piyali, but is momentarily distracted by an accidental push on the TV remote, which turns on a cartoon show she used to watch at Arnab’s house. Piyali frees herself and hides. But then, Rukhsana goes into labour, and Piyali, being a nurse couldn’t bring herself to kill her. She eventually helps Rukhsana have her baby, which is shown having an umbilical cord. Rukhsana leaves the baby to Piyali, while Arnab rushes to the old hut where Rukhsana goes back, injured and near-death. In her last breath, she tells Arnab that the baby isn’t like her and is human. The film ends with Arnab saying that Rukhsana’s love made the baby human, rather than Ifrit’s hatred.