Hannah Hutchinson never dreams of becoming an amateur sleuth, but when she makes the gruesome discovery of a murder victim in her school, she feels forced into the role. She becomes the prime suspect in the resulting murder investigation when a connection is found between her and the victim. Seeing the evidence against her unfold, she is compelled to investigate on her own. Juggling the everyday ups and downs as a teacher of children with disabilities, she now finds her every spare moment devoted to her determined search for the truth. As the mystery unravels Hannah finds that instead of crossing suspects off her list she is continually adding names - and as her search deepens, she begins to suspect even those who she thought she could trust. She sees motives for murder all around her and finds herself taking bigger risks as she follows the trail. Just as she begins to see progress in her investigation, Hannah discovers a clue that no one else is aware of. Hiding this from the detectives and knowing that it will implicate her even further makes her feel that she may be arrested at any moment. She stumbles along one step ahead of the police and when she finally figures out who the killer is, she comes to the frightening realization that the murderer won't hesitate to kill again.