When four students decide to combine a science report on caves with an environmental effort at Jacob's Well, near Wimberley, Texas, strange things begin to happen. First they find a stone engraved with a mysterious message. Forced to spend the night at the well site, where over the years eight divers have lost their lives exploring the underwater caves, they hear ghostly cries and strange guitar music. The message on the stone and other strange goings-on lure them into solving a mystery. But when a reclusive local character issues a warning to them, do they listen?