An inseparable couple Saira and Shiva find themselves in a complicated situation when a stranger claims to be her reincarnated lover from their previous lifetime, hellbent on destroying their relationship and winning her back.

The film opens with Shiv (Sushant Singh Rajput) moving from India to Budapest for a job as a banker, along with his friend Radha (Varun Sharma). Shiv is shown to have been a fun-loving womanizer back home and continues this behavior in Budapest. The audience is then introduced to Saira (Kriti Sanon), who is haunted by mysterious nightmares of drowning to death. She lives by herself in Budapest, working as a chocolate maker. Shiv happens upon Saira's shop while on a date with a woman, but finds himself deeply attracted to Saira. Though she initially rejects his advances, Saira eventually succumbs and sleeps with Shiv, revealing the next day that she actually has a boyfriend and does not want to betray him. Shiv interrupts one of their dates and shows Saira that she would rather be with him than with her boyfriend. Saira's boyfriend breaks up with her and leaves in a huff.

After this, Shiv and Saira spend a lot of time together and grow very close. On one of their nights together they go to a party with Radha, where they happen upon an eccentric psychic who knows about Saira's nightmares and tells her that her life is about to change drastically, that the events of her previous life will repeat themselves, and only she can fix them. Saira tearfully reveals to Shiv that she has a fear of water because her parents drowned after a car accident when she was two years old.

A few days later, Shiv proposes to Saira. She acknowledges that they have an inexplicably special connection, but suggests that they put their love to the test by meeting with other strangers and seeing if they feel the same type of attraction. They go to a party where Shiv flirts with multiple women. Meanwhile, Saira is charmed by Zakir (Jim Sarbh), a wealthy liquor baron. When Shiv comes over and meets Zakir, the tension is apparent but quickly dissolved. Later, Shiv tells Saira that he has to leave for Vienna for a week for a work commitment. Saira is upset to see him leave, but Shiv reassures her that this will only make their love stronger. While Shiv is gone, Zakir approaches Saira and she finds herself on a date with him. She tells Zakir that she finds herself drawn to him because he is exactly her type, but tells him that her heart belongs to Shiv. Zakir drugs Saira and kidnaps her, ordering his henchmen to kill Shiv. Saira wakes up and finds herself trapped at Zakir's mansion on an island off the coast of Croatia. She demands that he let her go, but he refuses, saying that he spent his whole life looking for her. He explains that they were madly in love in a previous life, but were separated. He refuses to let this happen again. When she refuses to believe him, he shows her a collection of uncannily accurate paintings he made of her at various ages. Thinking he is crazy, she attempts to escape but ends up falling into the ocean, which triggers her memory of her previous life.

Hundreds of years ago, Saira was the warrior princess Saiba (Kriti Sanon). She was in love with Kaabir (Jim Sarbh), a fellow warrior from her tribe. Their kingdom is threatened by the Muraakis, led by a wise old ruler (Rajkummar Rao). Kaabir is severely wounded by the fierce Muraaki warrior Jilaan (Sushant Singh Rajput), who gives Kaabir an ultimatum to surrender. Saiba challenges Jilaan, and they find themselves attracted to each other while they race through the woods. Saiba accepts defeat, surrendering the kingdom to the Muraakis and herself to Jilaan. Kaabir attempts to take Saiba back, but she reveals that she and Jilaan have fallen in love. On their wedding night, a comet falls and the Muraaki ruler realizes that this will be a fateful night. Kaabir ambushes Jilaan and Saiba. He murders Jilaan by wounding him and having him thrown in the ocean. Saiba jumps into the ocean to save him, but to no avail. When she herself dies in the ocean, Kaabir slits his own throat and dies. The Muraaki ruler forebodes that these events will repeat.

Having remembered everything, Saira agrees to marry Zakir if he promises to spare Shiv. Shiv returns to Budapest and cannot find Saira anywhere, when he sees the announcement of her engagement in the newspaper. He goes to their engagement party and sadly congratulates Saira, believing that she is marrying Zakir for his money. Later, they meet in secret and Shiv helps her escape the island. While they are being chased by Zakir's henchmen, Saira attempts to explain their previous lives to Shiv but he does not believe her. However, he remains steadfast in his conviction to be with Saira because he loves her. When they think they have safely escaped on a barge, a comet falls and Saira recognizes it as the same one from the fateful night in their previous life. Zakir ambushes them on the barge and has Shiv drowned, in a scene reminiscent of their previous deaths. This time, however, Saira is able to save Shiv when she jumps in. Zakir is killed, and the two soulmates are finally united.

The film ends with Shiv humorously telling their children to not believe Saira if she tells them any far-fetched stories about reincarnation, showing that he is still oblivious to the events of their previous lives.