In this twisty psychological thriller from #1New York Timesbestselling author ofThe Cellar, Emmy finds out that her twin sister, Iris, is trying to push her out of her own life—and might be responsible for their mother's death.After their parents divorced, 10-year-old twins Emmy and Iris were split up—Emmy lived with Dad, Iris with Mom. Now, after a tragic accident takes their mom's life, the twins are reunited and Iris moves in with Emmy and their dad. Devastated over Mom's death, Iris spends the first few weeks in almost total silence—the only person she will speak to is Emmy. Iris feels her life is over and she doesn't know what to do. Emmy promises her twin that she can share her life now. After all, they're sisters. Twins.It's a promise that Iris takes seriously. And before long, Emmy's friends, her life at school, and her boyfriend, Tyler, fall under Iris's spell. Slowly, Emmy realizes she's being pushed out of her own life....