The Teacher by Freida McFadden

Lesson #1: Trust no one. Eve has a good life . She wakes up each day, kisses her husband Nate, and heads off to teach math at the local high school. All is as it should be. Except… Last year, Caseham High was rocked by a scandal involving a student-teacher affair, with one student, Addie, at its center. But Eve knows there is far more to these ugly rumors than meets the eye. Addie can’t be trusted. She lies. She hurts people. She destroys lives. At least, that’s what everyone says. But nobody knows the real Addie. Nobody knows the secrets that could destroy her. And Addie will do anything to keep it quiet…