At the beginning of a stifling, sultry summer, everything shifts irrevocably when Lily doesn't come home one afternoon. Rachel is Lily's teacher. Her daughter Mia is Lily's best friend. The girls are fifteen - almost women, still children. As Rachel becomes increasingly fixated on Lily's absence, she finds herself breaking fragile trusts and confronting impossible choices she never thought she'd face. It wasn't supposed to happen like this.