Bea and Carter Kingsley's parents went missing 12 years ago while trying to uncover the mysteries of the mythical Saurmen and their keystones, which grant the owner tremendous power over all types of saurs. The clues in their parents' journals have led them to the Yucatan Peninsula, acquiring a troublesome Brachiosaur on their travels as well as Carter's pet Black Dwarf Tyrant, Buster. Meanwhile the villainous Viscount and his associates are also in the area, consorting with rebels plotting to overthrow the government and bankrolling a secret operation in the depths of the rainforests.