Burning Butterflies is a nihilistic psychological horror that revolves around the central theme of existential philosophical crisis. The movie explores the world of suffering and pain in a nihilistic manner, thus portraying the dire consequences that come because of certain actions in this uncertain world.

Srijani and Ranojoy are out for a trip out of Kolkata. The car reaches a deserted Bengal- Jharkhand border. The vast open field is covered with yellow dry grasses. In the wild and barren land Srijani and Ranojoy got involved in sex inside the car. After that they reach a petrol pump. While filling the petrol in the car, a very old service man comes closer to Srijani and whispers ‘Cthulhu Calling’. Here she also notices another person who kept looking at Srijani intensely. Unfortunately, on their way, their car breaks down in a completely deserted area. After waiting for long they happen to meet a police inspector, Prahlad who drops them to the sole nearby restaurant. There they have their lunch and look for a place to stay. They found an old castle, where they meet Indrajit Singh Deo who offers them the royal stay for couple of days. Srijani and Ranojoy get a wonderful stay for the time being.

But the story takes a different turn, when Srijani starts enjoying Indrajit’s company for having similar interest on art and culture. Indrajit’s mother stays there. He takes care of his mother and feeds her every day. He always have long conversations with his mother while feeding her, and from there we come to know about their past family history, how Indrajit’s ancestors used to torture the courtesans and other women badly. Indrajit loves his mother more than anything and from their conversation we come to know that he has developed soft corner for Srijani. Srijani gets deeply attracted to Indrajit from the very first day. Possessive Ranojoy gets jealous and starts reacting badly; first he gets drunk and slowly starts having fight with Srijani. And in the middle of all these, suddenly Ranojoy gets killed! His dead body is found in the middle of a forest. Prahlad keeps an eye on every one in these days. Prahlad interrogates Srijani and finds out that Ranojoy was actually not Srijani’s husband but an extra marital affair. Prahlad tells Srijani to stay in the palace and not to move till the investigation is done. Srijani gets very much scared in this situation.
In the middle of this disturbance Indrajit takes good care of Srijoni and gain her trust. He tells Srijani about the dark side of his family history, his lonely childhood and the disturbance he feels because of the curse and Srijoni promises him that she will never leave him.

Inspector Prahlad is carrying on his investigation on Ranojay’s murder case. He doesn’t take the case lightly and starts collecting information about people he doubts. He doubts Srijani, and interestingly one day he finds her searching something in the forest where Ranojoy died. In their conversations we come to know they were batch mates in college and Prahlad once had a crush on her.

One fine night police officer Prahlad takes advantage of visits Indrajit’s absence from the palace and visit his studio in the night and found a document of Carmel Institution. After that he goes to the palace for a thorough search but Srijani restricts him as Indrajit is a renowned and respectable person. Then Prahlad backs off and returns to the police station. Prahlad calls Carmel Institution London and comes to know that Indrajit is a psychopath criminal. He was an active member in a secret Cannibal Cult Society while staying in London. He was arrested there and was in an asylum for ten years. Now Prahlad understands this man Indrajit runs a big racket of porn films. After returning from the hunting, Indrajit comes to know that Police attempted to search his house. He understands that Prahlad is suspecting him and will catch him very soon. He tells Srijoni that he feels empty in Birsinghapur and wants to go Italy to start his career as an art curator. He asks Srijoni if she wants to go with him, she agrees. So Indrajit, suggests that they should leave immediately, Srijani agrees with his proposal and leaves with him that afternoon.
Prahlad visits Indrajit’s palace along with his subordinate Dinobondhu to save Srijoni from Indrajit but by then they already left. Prahlad informs the check posts to check Indrajit’s car so they cannot leave the border area. But nobody could trace them. After getting information from a local person, Prahlad goes to the jungle with his subordinate. They found Indrajit’s empty car and doubts that they might be somewhere near, probably underground of the castle.

Then audience find Indrajit in the underground chamber in completely different persona. Here the story reveals that Indrajit is sexually impotent and psychologically pervert. His mother is no longer alive, and he hallucinate his dog as his mother. The transgender person Shivendra assist him with all of his ritual practices. Indrajit has imprisoned many women in his underground chamber including Srijani and want to sacrifice them to Cthulhu on full moon to gain his sextual ability. After a long search, Prahlad finally finds the underground chamber. He tries to rescue Srijoni. In the fight with Indrajit, he gets injured but finally finds a way to escape with Srijani. After coming out of the underground chamber, they arrive in an open sand dune. But they end up sinking into quicksand. Indrajit watches their tragic death.