When Annie (Emmanuelle Vaugier), the alcoholic sheriff of a desolate New Mexico town, arrives at the scene of a mysterious accident, she is puzzled to discover a crab-like leg stuck to the grill of a burned-out vehicle. It later transpires that an archaeological dig has unearthed a murderous monster that's been trapped underground for 900 years and is now very, very angry with the human race. Teaming up with a group of stranded civilians, Annie must find a way to stop the beast before it wipes out everything, and everyone, in its path.