Sophie Hartley (Susan Sarandon) is convinced that she is being stalked. She becomes increasingly certain that her husband's (Sam Neill) beautiful co-worker, Mara (Emily Blunt), wants her children, her husband and her life. But no one believes Sophie. Forced to prove her sanity, Sophie grows increasingly paranoid - but is she imagining things? Sophie becomes completely caught up in her obsession, turning stalker herself - and makes a discovery more frightening than her worst fear.
索菲·哈特利确信她正在被偷偷的跟踪。她越来越肯定丈夫的漂亮同事玛拉想要她的孩子，她的丈夫和她的生活。但是没人相信索菲。迫使她去证明自己的神智清醒，结果却变得越来越偏执——哪些是她想象出来的事情吗？索菲完全陷入自己无法摆脱的思绪中，反变自己为暗中猎捕者——并发现了比她最担心的还令人恐惧的事实。