The protagonist, Natasha Kingsley, is the daughter of a Jamaican immigrant father whose DUI and resulting confession to the police has caused Natasha to face deportation. As the novel opens, Natasha is en route to the U.S. Customs and Immigration Services, where she meets an agent named Irene. Unbeknownst to Natasha, Irene plans to commit suicide later that day; Natasha writes her a "thank you" note that prevents her suicide. However, Natasha's mission to the U.S. Customs and Immigration Services office is ultimately unsuccessful, as she is re-directed to an attorney who cannot help her in the end.

Meanwhile, Korean-American Daniel Bae sees Natasha on a subway whose conductor is preaching about God. Daniel notices Natasha's "Deus Ex Machina" (God from the machine) tattoo. To him, she is a sign from God. The two become friends and swap stories. Natasha inspires Daniel to realize that he doesn't have to do exactly what his overbearing parents have in mind for him (viz. to attend Yale and become a doctor). Natasha and Daniel share only one day together, but it is a transformative one that causes each to reconsider what makes them happy. They aim to stay in touch when Natasha boards a plane to return to Jamaica with her family.

In a tidy tying-up of loose ends during the novel's final pages, Natasha sees Daniel on the same plane on which Irene (the agent from the Customs and Immigrations office) works as a flight attendant. Only in a novel by Nicola Yoon would such an elegant ending not seem contrived.

Yoon is a novelist who is notoriously adept at representing young love as the purest and least selfish variety; such a love, over time and distance, always prevails.

The novel invites its readers to consider the effect that individuals can have on one another beyond their acquaintance. Yoon herself is the daughter of immigrant parents, which renders this excellent novel partly autobiographical.