一群医学院实习医生某晚在医院附近酒吧玩乐时捉弄具有偷窥癖的医院清洁工肯尼斯(安德鲁-李•波茨 Andrew-Lee Potts 饰),并戏虐他为“疯狗”。被逼饮酒过量的肯尼斯癫痫发作昏厥,成为植物人,就要被终止治疗实施安乐死。倍感内疚的实习医生凯萨琳(阿莉尔•凯贝尔 Arielle Kebbel 饰)违反章程给肯尼斯注射了某种还在实验阶段的混合药物,试图让肯尼斯尽早苏醒,却没想到药物竟促成了肯尼斯灵魂出窍,附体到他人身上开始残忍的复仇行动。等到凯萨琳察觉出问题所在,却为时已晚,肯尼斯的灵魂早已脱离掌控,不管是陌生人还是朋友,甚至包括自己,凯萨琳还能相信谁?A young doctor in a US hospital administers a powerful and untested cocktail of drugs to a coma victim. But instead of curing him, it triggers a powerful "out-of-body" experience and enables the patient - a depraved and dangerous loner - to inhabit other people's bodies and, through them, take revenge on the bullying medical students who were accidentally responsible for his condition. The doctor, who was herself a part of this group, is also targeted and as her colleagues are singled out and relentlessly picked off, she realises that she can trust no-one - friend or stranger - as this comatose killer moves in and out of bodies at will, getting ever closer as his murderous supernatural powers increase.