Players of an outdoor treasure hunting game called Geocaching uncover the grisly clues left by a serial murderer on a nationwide killing spree. The murderer leaves obscure clues that the police don't connect. Players find these clues scattered around the country and write about them online. A couple in Austin, Texas begin to pull the clues together and a horrific picture begins to emerge. Will they identify and apprehend the killer before he kills again? Not before becoming targets themselves, when the killer joins the game and sets out a trap instead of a treasure.