In August 1947, 16-year-old Deepa's life in New Delhi begins to unravel in the days leading up to the birth of the Muslim minority nation of Pakistan, and the Hindu majority nation of India. Her secret Muslim boyfriend Amir, who sends her origami love notes, must now flee with his sister Layla and their parents to Lahore, Pakistan. Amir promises to return to Delhi to marry Deepa after the violence of Partition has ended. Soon after Amir's departure, Deepa's parents are killed. Her God-parents, fearful that Deepa is in grave danger, force her to move with them to London. Nine months later, Deepa gives birth to Vijay. She never sees or hears from Amir again.

After a devastating miscarriage in Atlanta in the present day, 40-year-old newly unemployed Shanthi ("Shan") Johnson must confront her husband Max about his reckless spending. While grieving both her pregnancy loss and her marriage's subsequent implosion, she finds clues that lead her to believe that the real reason her deceased father Vijay had abandoned her and her mother 30 years earlier to move to New Delhi was because he was in search of his father, a man he'd never known. To kickstart her life again, Shan moves out of her marital home, searches for a new job, and resumes her father's search for her grandfather, whose name, she later learns, is Amir. To find Amir, Shan must first track down her estranged 86-year-old grandmother Deepa, a prickly woman who never wanted to have anything to do with Shan. During Shan's search, which eventually takes her to Amsterdam and New Delhi, she comes to realize that the origami love notes Amir once sent to Deepa may be the clue to their reunion.