The sixth book in The Obernewtyn Chronicles. The time has come at last for Elspeth Gordie to leave the Land on her quest to find and stop the computermachine Sentinel from unleashing the deadly Balance of Terror arsenal. But before she can embark on her quest, she must find a lost key. And although she has long prepared for this day, nothing is as she imagined. Elspeth's search will take her where she never thought to go, and bestow upon her stranger companions than any she thought to have. It will lead her far from her destination to those she thought lost forever. And it will test her, as she has never been tested before.