Quantum mechanics, psychic powers and alchemy blend with adventure in an appealing read for fantasy and science- fiction fans alike. Silver Rivers is seven years old when her parents and younger sister disappear. Four years later, time becomes unstable and a school bus filled with children disappears into a time tornado while a wooly mammoth is spotted on the banks of the Thames. Silver has the central role in finding a mystical relic, the Timekeeper, which will resolve all the problems with time. The complex plot has many subordinate threads and plays itself out in two universes, rural England and above- and below-ground London. Well-developed main characters add liveliness and suspense to the story, while secondary characters (a pair of inept thugs, the original Schrödinger’s cat) add touches of humor to a basically sober story. The climax is chaotic and exciting; the resolution is realistic, bittersweet and a little too quickly achieved. Give this book to readers of William Sleator’s Marco’s Millions (2001) and Last Universe (2005), and Suzanne Collins’s Underland Chronicles. (Fiction. 10-14)