Walker of Worlds: Chronicles of the King's Tramp, Book 1 (Pearls of Sarah)

Jack, a Walker, has learned a secret-one that could mean the end of all the worlds, not just his own. He has earned an enemy-and the Mage of Four, Mage of Luck, is a powerful enemy indeed. Jack must flee to our world, where he gathers a small group of unlikely, sometimes unwilling allies. In the ultimate confrontation, their efforts will determine the fate of the universes.