Phoebe is the youngest Oppenheimer sibling, the eponymous latecomer and, although the reader does not find out until later, the narrator of the story. Because she visits each person connected to the Oppenheimer story, she can also narrate scenes and thoughts she was not present for with a degree of omniscience. Phoebe is the driving force behind the narrative, and as the first-person narrator, often obliquely foreshadows future events.

As she grows up, Phoebe struggles with the idea that she missed the best time of her family. By the time she is old enough to be a part of things, the family has been destroyed. Phoebe grows up in the aftermath, with only Lewyn, who moved home partly in order to care for her. His revelation that her embryo was fertilized at the same time as the other siblings reinforces the sense that, as a character, Phoebe possesses wisdom and compassion that go beyond her age. As well, she is the missing piece of the family, and her presence is necessary to make them whole.

Phoebe’s journey begins with the letter she reads from the American Folk Art Museum. When she goes to Lewyn for answers, he offers new information about her own birth.