When Cassie Fitzgerald was at school in the late 90s, she and her friends killed a fellow student. Two decades later, Cassie is a happily married mother who loves her job—as a police officer. At Cassie's high school reunion, controversial MP Garfield Rice is found dead, supposedly from a drug overdose. The investigation is high profile, and headed by Cassie's new boss, DI Harbinder Kaur. After another body is found, Cassie has the uneasy feeling that one of her old classmates has killed again.