Four American friends on vacation in Cancún, Mexico—Jeff, Amy, Eric and Stacy—meet a German tourist, Mathias, who persuades them to join his hunt for his younger brother, Henrich, last seen headed off with a new girlfriend toward some ruins. The four soon regret their impulsive decision after they find themselves lost in the jungle and freaked out by signs that they're headed for danger. Smith builds suspense through the slow accretion of telling details, until a deadly menace starts taking its toll, leaving the survivors increasingly at each other's throats.