What the Fireflies Knew is a 2022 coming-of-age novel by Kai Harris. The novel traces how KB, a 10-year-old Black girl, matures during her summer stay with her grandfather. KB grows to accept the imperfection of adults in her life, recognizes the power of prejudice, and gains confidence in her ability to meet the challenges life throws at her.

This guide is based on the 2022 Kindle edition from Tiny Reparations Books, an imprint of Penguin Random.

Content Warning: This novel includes a racist slur used to refer to Black people. The slur is not represented in the guide. This novel also includes direct presentation of sexual assault, indirect presentation of child abuse, and references to substance abuse and death as a result of substance abuse.

Plot Summary

It is January 1995. Detroit native Kenyatta Bernice, known as “KB” to her family, is 10 when her father dies of a drug overdose. She discovers his body one morning. As the police search her house, she gets her first inkling that his death isn’t from natural causes. After his death, the family experiences financial hardship. When Jacquee, KB’s mother, is no longer able to pay their bills, the family loses their home and lives in their car. Jacquee eventually earns enough money from her job to rent a hotel room for her family. Nia, KB’s older sister, and KB continue to go to school, but Nia begins to act out. Unbeknownst to her mother, Nia confronted her father about his substance abuse after classmates teased her, and her father struck her during the confrontation.

Unable to handle so many stressors at the same time, Jacquee leaves her children in Lansing, Michigan, with her father, from whom she became estranged as a teenager. KB feels sad and abandoned when her mother leaves. Jacquee doesn’t give her daughters any indication of when they might return to Detroit. She is keeping it secret from her daughters that she will be entering a residential treatment facility to address her depression.

KB doesn’t care for her grandfather at first. He is a quiet man who feeds her but doesn’t acknowledge her otherwise. KB plays outside and reads her comfort book—Anne of Green Gables—to deal with her boredom and fear. KB’s relationship with her grandfather improves when he shows her that the secret to catching fireflies is to move slowly and subtly. When she realizes that he has the financial means to treat her to books and dresses, things she rarely got at home, she hatches a plan to reunite her family by getting her mother to move in with Granddaddy. Her plan is stymied both because Jacquee is by now in the institution—a secret KB learns by eavesdropping—and because Jacquee and her father refuse to reconcile.

KB also passes the time by befriending Bobby and Charlotte, two white children who live in a newer, nicer home across the street. Her grandfather warns her away from the children because he believes (correctly) that their mother has racist ideas about Black people. KB plays outside with the children despite her discomfort with their curiosity and assumptions about her. KB also learns more about her extended family when her grandfather takes her and Nia to the family barbeque on the Fourth of July. KB also encounters Rondell, an older cousin who claims he is her age. KB discovers Nia and one of the cousins kissing and fondling each other. She doesn’t share what she saw with her grandfather, but her inability to understand what Nia was doing and why further damages the relationship between the sisters.

Later that month, KB experiences her first birthday away from her mother. The birthday is spoiled when KB tries to get Rondell to do what Nia and the cousin did at the barbeque, but KB’s grandfather interrupts them just as KB is having second thoughts. He warns her that she is of an age when love and desires mount. It is important that she be mindful of the intentions of boys. He also tells her to know her own boundaries when dealing with boys.

A series of conflicts force KB to assume more control over her own life. When she shares with Bobby and Charlotte the truth about her father, being unhoused, and why she is living with her grandfather, their reactions hurt her. She asks Charlotte to borrow her bike so that she can run away. She encounters Rondell, who sexually assaults her after promising to take her to a safe spot while she is on the run. When KB returns home, Charlotte’s mother yells at her and accuses her of being a thief because her children told her about KB’s background. Her grandfather defends her. KB chafes against stereotypes and comes to believe that her grandfather was right to warn her about playing with the white children.

After Nia confronts her grandfather about the truth behind why they lost their house—their father’s debts—the two girls finally share their secrets. During a phone call with KB, Jacquee shares the truth about the fight that ended her relationship with the girls’ grandfather. Granddaddy struck her and accused her of trading sex for a photo session. She encourages KB to realize that there is no such thing as perfection and that people must learn to work toward reconciliation after they make mistakes. KB takes both her sister and her grandfather into her confidence about the plan to reunite the family. Ultimately, Granddaddy gives Jacquee a down payment to buy her own house. Although this isn’t quite the ending for which KB hoped, it is a realistic one. Through all that she has learned that summer, KB emerges as a more resilient and mature girl.