只身一人漂泊在外的女孩杰西卡（Lilly-Fleur Pointeaux 饰），自童年时代起就饱受同一个噩梦的困扰，梦中她总能看到一个马头人身的怪物，对方手执锋利的武器凌虐着创伤的无辜女人。这天她照例从噩梦中惊醒，随即接到妈妈打来的电话。电话中她得知外婆罗丝（Gala Besson 饰）去世，妈妈希望她能回来参加葬礼。带着种种复杂的情绪，杰西卡总算回到了阔别三年之久的家乡。继父吉姆（Murray Head 饰）热情地将她迎进家门，而母亲则始终不改强势固执的态度，母女的争执在所难免。与此同时，她的噩梦愈演愈烈。 按照研究心理学的男友肖恩书中的指示，杰西卡决定主动进入梦中，去探寻噩梦产生的根源……Since her childhood, Jessica has been haunted by recurrent nightmares whose meaning escapes her. This peculiarity has led her to study the psychophysiology of dreams and to follow a therapy with Sean, her mentor and boyfriend, to try and understand the origin of her nightmares. Following the death of her maternal grandmother she hardly knew, Jessica reluctantly returns to the family home. She doesn't get along with her mother very well and is not looking forward to seeing her again. Upon her arrival, Jessica discovers that her late grandmother is lying in the adjoining room to her own during the wake. After a rough first night made restless by a strange nightmare in which she meets her dead grandmother, Jessica suddenly becomes ill. Stuck in bed with a high fever, the young woman decides to use her lethargic state to try out lucid dreaming. In order to do so, and on Sean's advice, Jessica breathes a little bit of ether whenever she needs to sink deeper into the other world to try and take control of her nightmares. Jessica then begins to wander in a nightmarish world inhabited by twisted versions of her family members. She gradually improves her skills as a lucid dreamer and investigates to solve the mystery that gnaws her and haunts the family home...
