[2] The film is inspired by the 2008 Noida double murder case, which was met with some criticism by Rajesh and Nupur Talwar.

[4][5] Remy Fernandes, a house maid, is seen praying in the servant quarters of Dr. Sachin Mahajan's plush duplex flat in Mumbai.

Hansal, who lives in the building right across the Mahajans', sees Riyaz enter the house one night, and deliberately calls Sachin to inform him.

In a drunk state, and unable to control his anger, Sachin attacks Riyaz with a surgical knife, injuring him on the arm.

Paraskar also discovers missing servant Chetan's dead body concealed within the floorboards of the Mahajan house, adding to the mystery.

He meets her mother, who points out to a picture of a younger Remy, and the pieces finally fall in place, ending the investigation.

At the hotel, Sachin's dead body is found and the local police conclude that he committed suicide due to the guilt from the case.

However, Paraskar is not convinced and summons Aarti, Remy, Brinda, Hansal, Riyaz's parents and local police officers to the Mahajan house, where Ayesha was killed.

Finally, Paraskar reveals that Riyaz and Sudhakar Mishra were killed by a corrupt local policeman, who was being bribed by Aarti.

[7] The production, along with two similar proposed films by different filmmakers, was met with some criticism by the Talwar family, who stated that they would seek legal recourse against any media adaptation of the murder case.

[8][9] Gupta later responded to this by stating that the film was intended to be a complete work of fiction and that he did not use any of the real names of people involved with the murder.

[12][13] The Talwar family initially requested permission to screen Rahasya before it released to the general public and upon receiving no response from Gupta or the production company, filed a case against the film stating that they felt that it would potentially distort facts about their daughter's death.