Annabelle Cartier, the school's youngest teacher, is an avid online dater. During a date, she rejects an unstable young man, who is now fixated on her. Frightened by his harassment, she calls the police, which doesn't discourage the lovesick man. On the last day of term, he manages to enter Annabelle's classroom and, armed with a revolver, takes the students and their teacher hostage.