In the fourth installment of this stunning series, the King family plummets into head-spinning action, as the house and the worlds that lay beyond grow increasingly dangerous. David, Xander, Dad, and Keal have discovered a secret. Now, finding Mom a small part of their mission. Using the portals to build an empire, Taksidian wants the house. The consequences of his meddling beyond the famil- to the future of the world itself.

The Kings know their survival depends on stopping the bloodthirsty assassin. They must find his weakness. Most startling is their ability to change the path of history. Will tinkering reunite the family and save the future . . . or set humankind on a course of potential destruction?