A young woman named Victoria (Shannyn Sossamon) is invited to visit her sister (Alecia Moore) in Paris and gets a trip she wasn't counting on. After her arrival they go to a party that's down in the catacombs of Paris and they tell her of a story about a deranged killer who stalked the passageways, killing people. She's a jumpy, high-anxiety person, so the story terrifies her. After she and her sister are attacked and her sister is killed, she runs away and gets lost in the labyrinth. She meets Henry, a fellow party goer, and helps her in her quest to leave the tunnels but he gets injured and she's forced to leave him behind with a broken leg.
The movie starts off as one thing and then ends as another, with a completely unexpected twist that works and makes the situation even more terrible.