A Princeton-educated art historian and librarian, Belle is the child of a barrier-breaking father and a beautiful mother descended from the elite Fleet family. Her character is based on the historical figure by the same name who lived from 1879-1950. The novel traces how Belle transforms from the daughter of a light-skinned Black family to passing as a white woman who curated the collection that became the Pierpont Morgan Library. As a white passing Black woman, Belle’s understanding of the costs and gains of passing and choosing career over love evolves over the years.

In flashbacks, the authors reveal that Belle’s decision to pass came after her parents separated because Genevieve, Belle’s mother, saw the rising Jim Crow laws of the post-Civil War United States as a direct threat to her family’s survival. In the contemporary moment of the novel, Belle is motivated to agree with this plan because it will allow her to work with the art and books she so loves. When J.P. Morgan hires Belle, despite her youth and gender, Belle’s life changes.

Because of her mother’s laser focus on Belle successfully passing and her siblings’ inability understand the psychological cost of passing, Belle feels deep resentment towards her family.