That's what Eric Scott always thought. But that was back before he learned about the Hallway of Worlds and the sparkling mist. Now, after three Assignments to save other worlds, he's not so sure. When the Gatekeeper tells him someone might be using the mist-matter from failed worlds-to change the past on Eric's world, possibility becomes probability.

In their fourth and final Assignment, the Deliverers-Eric Scott, Stig the owl, Kate Endria, and Hallo Tosis the dwarf-face a challenge like no other. They must prevent the worlds they have helped on their previous Assignments from being wiped out. They are sent back in time to the American Revolution to stop an unknown foe from using the sparkling mist to change history. Worlds, the Hallway and the universe as we know it, hang in the balance. Will the Deliverers be able to contain the sparkling mist once and for all, or will everything they have achieved so far be annihilated?