Plot
Vaani is waiting to get married to her college boyfriend Mahesh at the courthouse, but he calls to inform her that he is leaving her to marry a rich businessman's daughter to climb up the social ladder. She faints away after the news and wastes away into depression, giving up her writing
Six months later, she joins Buzzlist as an intern and meets Krish Kapoor, an aspiring musician stuck in his past and abusive childhood and battling with anger. Krish faces multiple setbacks in his musical career, including disputes with journalists, and a row with his band, but KV, his best friend, helps fund the band, although Krish's education is at stake. Krish returns a notebook of poetry accidentally left behind by Vaani at the publishing house and assaults a journalist, and becomes infatuated with her writings.
Although initially wary of Krish's moody nature, Vaani agrees to work together on a song for hip-hop singer Prince. Krish helps her to overcome a block and finds torn pages of her notebook at the cricket playground where he spends his time alone, and she begins to write again. Krish and Vaani slowly become close, and Vaani's world settles into a routine.
However, after Krish confronts his alcoholic father, Vaani comforts him and convinces him to enter rehabilitation, but Krish is forced to give up the credit for their project to pay for his father's rehabilitation, and he pushes Vaani away, believing she deserves better. They meet again at Prince's concert, where Krish confesses his love for her, and they begin dating, and Krish finally reconciles with his band.
Vaani's parents start worrying that Krish will harm Vaani like Mahesh did and confront Krish at the hospital after Vaani faints, but they reluctantly agree to let him continue seeing Vaani after Krish promises to do so. However, they are faced with the devastating news that Vaani has early-onset Alzheimer's disease, and Krish has to quit his job to care for her, and on the advice of doctors, they move to a guesthouse in Alibaug to make new memories.
At a later concert, Mahesh tries to assault Vaani, but Krish jumps to her aid, and she, in confusion, stabs his right arm and has a severe breakdown. At the guesthouse, Krish's father reconciles with him, and in one quiet moment, Krish plays a piano tune for Vaani, but she mistakes him for Mahesh and offers to write the words for his melody; Krish leaves to inform his crew that he is quitting the band to care for Vaani, but when he gets back, Vaani has vanished. Krish discovers her diary with the words to the song she named "Saiyaara" and records it in her memory before releasing it to the world, where it goes viral, catapulting him to fame and making him reconcile with his band. He continues to tour the country with Vaani's writings.
A year later, KV finds a fan video of Vaani singing along with one of Krish's songs that went viral, and Krish tracks her down to an ashram in Manali. A letter she has written him reveals that she has fled to Manali to avoid hindering his music career after recalling the incident at the concert but has continued to follow him, although she doesn't recognize Krish, but he gently reminds her of their time together at the cricket playground. Vaani's memories of their time together slowly return, and she says that she loves him, but Krish leaves her at the ashram, promising to come back. The film ends with Krish performing at Wembley Stadium with Vaani by his side as they get married, and Vaani continues to write her thoughts about the wedding.
