Starr Carter is a 16-year-old African-American girl who lives in the predominantly black neighborhood of Garden Heights and attends a predominantly white private school called Williamson Prep.
After a firearm is discharged at a party Starr is attending, she is driven home by her best friend, Khalil. They are stopped by a police officer for failing to signal at a lane change. The officer barks orders at Khalil. Khalil disagrees with the officer, who instructs him to exit the car.
While outside the car, the officer retrieves Khalil's driver’s license and instructs him to keep his hands on the roof. Khalil leans down into the car window to check on Starr before reaching through the driver side to pick up a hairbrush. The officer, thinking that Khalil is reaching for a gun, shoots and kills him.
The killing becomes a national news story and causes a town-wide protest against racial injustice. Starr's identity as the witness is initially kept secret from everyone outside her family – leaving her friends, Hailey Grant and Maya Yang, and her boyfriend, Chris, who all attend Williamson Prep, unaware of her connection to the killing.
Starr agrees to be interviewed on television and to testify in front of a grand jury. While defending Khalil's character during her interview, in which her identity is hidden, she names the King Lords, the gang that controls her neighborhood. The gang retaliates by threatening Starr and her family, forcing them to move in with her Uncle Carlos, her mom's brother, who is a police detective.
Carlos was a father figure to Starr when her father, Maverick, spent three years in prison for a crime he did not commit. Following his release, Maverick left the gang and became the owner of the Garden Heights grocery store where Starr and her half-brother Seven work. Maverick was only allowed to leave the King Lords because his false confession to a crime kept gang leader King from being locked up. King, who is widely feared, now lives with Seven's mother Iesha, as well as Seven's half-sister Kenya, who is friends with Starr, and Kenya's younger sister Lyric.
After a grand jury does not indict the officer, Garden Heights erupts into both peaceful protests and warlike riots. In reaction to the decision, Starr takes an increasingly public role, including speaking out during the protests. Her increasing identification with the people of Garden Heights causes tension with her school friends, especially between her and Chris. Starr and Maya start standing up to Hailey's racist comments, breaking up their friendship, and Chris remains supportive of Starr.
Starr and Seven get trapped in Maverick's grocery store, which is fire-bombed by King and his gang. The two escape with the help of Maverick and other Garden Heights business owners. The community stands up against King, who goes to jail. Starr promises to keep Khalil's memory alive and to continue her advocacy against police violence by "any means necessary".
