It is the message every parent of a school-age child fears: “Active Shooter on Campus.”

Jack Swyteck is at his office when he receives the emergency text from Riverside Day School. Both his daughter, Righley, and his wife, FBI agent Andie Henning, are in danger. Andie is in the school’s rec center when she hears the fire alarms, then loud popping noises and screams coming from the hallway. A trained law-enforcement officer, Andie knows she’s supposed to stay locked down inside the room. But Righley is in her kindergarten classroom and Andie must get her to safety.

The tragedy prompts mass hysteria—and dangerous speculation. The police haven’t identified the shooter, but they find a handgun on the school grounds registered to a parent, a Muslim man named Amir Khoury. News of the gun and its owner leaks and quickly goes viral. Within minutes Al Qaeda claims responsibility. Andie is shocked—Amir is married to her friend, Lilly, a WASP whose bloodline goes back to the American Revolution.

When Xavier, Amir and Lilly’s oldest child and an eighteen-year-old senior at Riverside confesses to the crime, the local community’s anti-Muslim fervor explodes to levels unseen since 9/11. Terrified for her son’s life, Lilly asks Jack to step in. A seasoned defense attorney with a passion to see justice done, he’s taken on plenty of complicated cases. Xavier’s, however, is not one he’s inclined to take—until an old friend who lost his daughter in the shooting tells him that he must.