在父亲的生日宴会上，一面镜子的突然碎裂让吉娜（琳娜·海蒂 Lena Headey 饰）和众人感到了深深的不安。第二天，吉娜来到工作的医院，却被告知就在不久之前自己刚刚离开了医院。对于这一异象，吉娜只以为是同事眼花，但之后发生的事情却让她再也无法保持平静——无论是大街上正在行驶的红色越野车，还是车中所坐的女子，皆和吉娜完全相同。 　　无法控制自己好奇心的吉娜尾随女子来到了一幢公寓，过后，吉娜遭遇了惨烈的车祸。为了疗伤，吉娜开始和男友斯蒂芬（梅尔维尔·珀波 Melvil Poupaud 饰）同居，她将她的所见所闻告知了男友，后者却认为她不过是脑部受到了创伤，吉娜陷入了无尽的恐惧和怀疑之中。In London, the radiologist Gina McVey organizes a surprise birthday party to her father John McVey with her boyfriend Stefan Chambers, her brother Daniel McVey and his girlfriend Kate Coleman. On the next day, she sees herself driving a car on the street and she follows the woman to her apartment, where she finds a picture of her father and her. While driving back, she has a car crash and loses parts of her memory; further, she believes Stefan is another man. Gina decides to investigate what is happening and unravels a dark reality.