Beyond a Black Hole — Karen Hutchins Pirnot

Eilla and Allie Henderson arrive back on Earth to the shocked presence of the science team who sent them on their galactic adventures. They team up on a science project and begin to solve the ancient mysteries of the disappearance of the continents Mu and Atlantis. As a reward for their award-winning science project, the girls are treated to a scientific expedition to the lost world of El Mirador in northern Guatemala. There, they confront creatures who help the girls to put together pieces of an ancient civilization puzzle. When Eilla is returned to her own universe, an exotic creature appears, claiming to have the answers to age-old theories of civilization.