Eleven years ago, a cave-in on the north side of a mine trapped six miners. Six days later, rescue teams found five dead miners and the comatose Harry Warden (Richard John Walters), who survived by killing the other miners with a pickaxe. Tom Hanniger, the mine owner's son, was blamed for the mine disaster because he forgot to vent the methane lines.
The following год on Valentine's Day, Warden wakes from his coma and kills many people. At the abandoned mineshaft that was the site of the disaster, a party is in full swing, attended by many teens, including Axel Palmer (Kerr Smith), his girlfriend, Irene (Betsy Rue), Tom Hanniger (Jensen Ackles), and his girlfriend, Sarah (Jaime King). Sarah goes in alone and gets Остаться в живых looking for Axel and Irene. She runs across a teen and a few секунды later he is killed. She is confronted by Warden in full miner's garb, carrying a bloody pickaxe, and she flees. Axel grabs her and they, along with Irene, hide from the killer. Warden eventually sees the trio, and they run out of the mine, meeting Tom as he comes in. The killer hits Tom with the pickaxe, injuring him, while the other three run for the car and leave Tom behind. Tom runs back into the mine in an attempt to escape Warden. Before Tom can be killed, the police arrive and shoot Warden, who makes his getaway back into the mine.
Ten years later, Tom's father, from whom Tom has been estranged, dies and Tom inherits the mine. Tom returns to town after his father's funeral to sell the mine. Axel is now sheriff and married to Sarah, but he is cheating on her with Megan (Megan Boone), who works with Sarah at Sarah's grocery store. After Megan and Axel have sex at his family's old house in the woods, Megan tells Axel that she is pregnant with his child.
Meanwhile, at the motel where Tom is staying, Irene, the motel owner (Selene Luna) and a trucker (Todd Farmer) are murdered. Later, Tom visits his newly inherited mine. In the mine, Warden appears and forces Tom into a cage; Warden bends the metal latch on the door, making Tom's escape impossible. Warden then murders William "Red" Kirkpatrick (Jeff Hochendoner) the miner who was accompanying Tom. Before the rest of the mining crew arrive, Warden flees, and suspicion falls on Tom, despite the fact that he was locked in a cage the entire time. Axel then asks Jim Burke (Tom Atkins), the retired sheriff what happened to Warden. The retired sheriff says that he and Ben Foley (Kevin Tighe), the mine manager killed and buried Warden, but when Axel, Tom, and Sarah go to the burial spot, Warden's body is no longer there.
Next, Ben Foley and Megan are killed. The killer than goes to Axel's house and kills Axel's son's baby-sitter Rosa (Joy de la Paz) and Jim Burke who was trying to catch him. Tom tries to take Sarah to Axel's house in the woods to convince her that Axel is the killer. Axel calls Sarah while she and Tom are on the road; Axel tells her that Tom has been in a mental hospital and is the killer. Sarah crashes Tom's car and makes her way to Axel's old homestead. She is chased by the killer all the way to the mine. Sarah goes into the shaft where the original murders took place. She is joined by Tom and Axel, and, after a brief stand off between the men, Axel and Sarah realize that Tom is delusional. A montage then plays out all the murders in the film again, revealing Tom to be the killer. Tom committed the murder in the mine, then locked himself in the cage, hallucinating Warden as his nemesis. Sarah shoots a tank and causes an explosion, triggering a partial cave-in. She and Axel escape, believing Tom to be dead. A rescue team enters the mine to look for survivors, but Tom kills a rescue worker and escapes the scene dressed in that worker's uniform.