佩妮（苏珊·斯塔丝伯格 Susan Strasberg 饰）的父母在她很小的时候就离婚了，一直以来，佩妮都跟着母亲生活。一场意外夺走了母亲的生命，于是，孤苦无依的佩妮接受了父亲的邀请，前去和父亲以及继母一起生活。然而到了父亲家，佩妮却发现在那里的只有继母一人，虽然这个女人表现得非常的和善与热情，但佩妮还是对她充满了戒备。继母家里发生的各种诡异的事情，以及始终下落不明的父亲让佩妮的神经越来越紧张，渐渐地，她开始分不清，在这里经历的一切，究竟是不是自己的幻觉。很显然，继母也希望佩妮产生这让的自我怀疑Penny Applebee's parents were divorced when she was quite young and she grew up with her mother. After her mother's death, the wheelchair-bound Penny has accepted her father's invitation to live with him. She arrives only to learn that her father is away though her stepmother - who she is meeting for the first time - proves to be quite welcoming. On her first night however, she sees a light in the summerhouse and upon investigation, sees her father sitting there, apparently dead. Others can find nothing there and tell her she must have imagined it. She later sees his body in library and then again in the pool. She comes to believe that her stepmother and her father's friend, Doctor Pierre Gerard, are plotting to drive her insane. She gets a sympathetic ear from Bob, the chauffeur, who feels there has to be some rational explanation for what has been happening.