A dagger made from a giant snake tooth sends Alex and Amber Brody on the adventure of a lifetime. Amber believes the giant snakes still exist somewhere. Investigating the dagger leads them to the Mayan city of Chichen Itza and the legend of their serpent god Kukulkan. Meanwhile, Amber is experiencing changes that they discover are caused by her DNA having been fundamentally altered somehow. All the while, the mysterious Guardians are watching, waiting for the right moment to strike. If they can survive giant snakes, can they survive the Guardians too?