What they needed was an expert to go back to the Empty World and find the lost grown-ups. What they had was Christy.With the ever-faithful Trevor in tow, Christy defies her mother's wishes and ventures...

Defend the portals. Defend the universe.Sent back to Earth, Christy bides her time plotting to go back to the Empty World. She has the means; she just needs to round up as many friends as she can and...

A missing Grandfather. Two missing friends. A forbidden rescue plan.Christy's parents forbid her from returning through the portal, but her grandfather is still stranded in the Empty World. When Danny...

They said her grandfather was dead. They said her grandmother was crazy. Christy knows they're wrong.When her grandmother dies, 13-year-old Christy inherits an old family secret: the pond behind her house...

Lost technology might let him walk again, but he'll need lost friends to help him get home.Cory delves into the Empty World all on his own with just a computer generated guardian for an ally. He knows...

Plunge into the pond and land in an alien world.When her grandmother dies, 13-year-old Christy inherits an old family secret: the pond behind her house is in fact a portal to another world. What's more,...