Straight-A student Lily Jeong, misunderstood by helicopter parents and ignored by thoughtless classmates, sneaks her manipulative boyfriend into Rockwell High believing he’ll get revenge for her recent public humiliation. But he breaks his promise that no one will get hurt, and minutes later, fourteen people are dead.

Plagued by guilt, Lily invents one lie after another to evade arrest. While devastated survivors grieve, investigators make slow progress identifying the accomplice, and class president Keisha Washington—Lily’s long-time nemesis who narrowly escaped death—resolves to hunt down the culprit herself. As Lily dodges detection, she bonds with Sofia Hernandez, who lost her best friend, Caitlyn Moran, in the shooting.

The adults around them—Joe Hernandez, Sofia’s father, and the first policeman to enter the school; Charmaine Robinson, a nurse whose husband died protecting Keisha; and former Army Colonel Mike Moran, Caitlyn’s father—also struggle to piece together their wrecked lives. When they come together in a support group, instead of finding solace, their mounting feelings of grief and anger drive them to protest and vengeance. Will they ever find justice and peace?