Three college students, Ryan, Jake, and Erica, set out to film a great horror movie for one of their class projects; but during filming, something goes terribly wrong and the students suddenly find themselves in their own worst nightmare. Some of the events are caught on tape by the camera that Jake continues to record with, a camera that is later retrieved by two detectives, Adams and Dalton. It's now a race against time, and the detectives must use the video to rescue the students. As the case goes deeper, the detectives eventually find themselves in the middle of a dense forest on the outskirts of town, and what they uncover is far worse than what they could have ever imagined
八公（Forest 饰）是一条谜一样的犬，因为没有人知道它从哪里来。教授帕克（理查·基尔 Richard Gere 饰）在小镇的火车站拣到一只走失的小狗，冥冥中似乎注定小狗和帕克教授有着某种缘分，帕克一抱起这只小狗就再也放不下来，最终，帕克对小狗八公的疼爱感化了起初极力反对养狗的妻子卡特（琼·艾伦 Joan Allen 饰）。八公在帕克的呵护下慢慢长大，帕克上班时八公会一直把他送到车站，下班时八公也会早早便爬在车站等候，八公的忠诚让小镇的人家对它更加疼爱。有一天，八公在帕克要上班时表现异常，居然玩起了以往
