Sarah Goldman, mother to six-year-old Jacob, is relieved to move across the country. She has a lot she wants to leave behind, especially Holly Monroe, the pretty twenty-two-year-old babysitter she and her husband, Daniel, hired to take care of their young son last summer. It started out as a perfect arrangement—Sarah had a childminder her son adored, and Holly found the mother figure she’d always wanted. But Sarah’s never been one to trust very easily,…