Gabriella Mallory, AP student and perfect-daughter-in-training, stands barefoot on a public toilet for three hours while her school is on lockdown. Someone has planted a bomb, and she is hiding. The bomb is defused, but the would-be bomber is still at large - and everyone at Central High School is a suspect. The school starts a top-secret crisis help line, and Gabi is invited to join. When she does, she is drawn into a suspenseful game of cat and mouse with the bomber, who has unfinished business.