Igniting real fear, 1920 London is a horror movie. The movie is set in the typical Rajwada set up in Rajasthan and also in London. The film opens into the life of Shivangi, princess of a Rajasthan royal house (in Sikar), now living in London with her husband Kunwar Veer Singh. They make a happy home until one day when Veer develops a minor illness that soon flares up into a wasting disease shrivelling his body and shrinking his head. Veer is hospitalized and his symptoms worsen - his body begins to contort unnaturally and he begins growling in strange languages. The doctors seem to diagnose it as tetanus (no cure available). Shivangi is frightened; Veer is just not the same and Shivangi's handmaiden, Kesar Ma, quickly calls it black magic.
Kesar Ma thinks it is because of Veer's father, the King, had two wives and the second wife wanted Veer, the heir, out of the way. The film moves to Rajasthan. Shivangi with her family visits an exorcist for Veer's condition. This exorcist attempts to confront the witch by entering the other realm (through a mirror) but is soon thrown out, too powerless for the witch. The exorcist refers the King to the most powerful spiritual master in the land, Mewar Baba, also known as Jai Singh Gujjar. In other parts of Rajasthan Jai Singh Gujjar (Mewar Baba) a former convict, arrives and successfully performs the exorcism on a girl possessed by an evil spirit.
Shivangi shudders on hearing about Jai. She was deeply in love with Jai some years ago. Her uncle saw them together and tried to blackmail the helpless and beautiful Shivangi into sleeping with him. Jai stepped in between and fought off the uncle who promptly reported the matter to the King. Jai was charged with attempted murder. Shivangi inexplicably stood as a witness against Jai and Jai was ultimately sent to jail for five years. Now Shivangi has come back to ask Jai to help her save her husband. Jai flatly refuses but Shivangi pleads and persuades him. Jai finally agrees to come to London.
Jai investigates the matter and discovers that Veer's troubles began upon receiving a strange amulet as a gift from an unknown admirer in Rajasthan. The amulet transmitted the witch demon into Veer. Jai prepares Shivangi into reciting a spiritual chant to bind the witch to their mansion so Jai can throw the locket into the river Thames, thereby freeing Veer. Shivangi maintains the chant over the witch's attempt to thwart it and Jai finishes the job. But it is revealed that the amulet and the witch were actually dispatched by Jai! As Jai prepares to leave London, Shivangi confronts him. (How did he know the amulet came from a specific person?) Jai admits his vengeance saying that he wanted Veer dead. Shivangi reveals why she had betrayed him many years ago. When their affair was revealed the King had ordered Jai killed. Shivangi begged for his life and it was granted for the price of her betrayal. Now guilty and dismayed, Jai resolves to stay in London and free Veer from the witch.
Jai prepares his final assault on the witch. Jai invokes his own spiritual master through a letter. The master chastises Jai for acting in haste and then regretfully says that the witch will not leave without taking a soul. The master directs Jai to an abandoned church where he receives a set of charmed Celtic daggers. Jai prepares a charm to attack the witch. He enters the witch's realm and recovers the amulet. The witch attacks ferociously and is about to stop Shivangi when Jai smashes the mirror (thus closing the portal) so Shivangi can burn the amulet and free her husband. Shivangi sees Jai smile peacefully as Veer comes to life. Some weeks later, Veer and Shivangi find the letter of correspondence between Jai and his master. Jai had offered his soul so Veer could be freed. Veer is touched and places Jai's photograph upon his mantelpiece as the film ends.