When Micki Silver--a moody 11-year-old--stands in what she discovers too late is a magic room and wishes she'd never been born, she's cast back 100 years to when Gregory, a boy who would become her great-great-grandfather, lies dying from an accident. The author weaves a complex tapestry here; shepherded by a mysterious old egg-woman (or maybe more than one) who utters cryptic warnings about branches and trees, Micki passes back and forth between the 1890's and the present, meeting several of her forebears and trying to figure out how to save Gregory and keep her wish from coming true. In the end, a small magic ritual plus a firm new wish do the trick. Williams ties up most of the loose ends but leaves a major one dangling by never revealing the old woman's identity or the source of her interest in the Silvers. Still, though its internal logic is not as well developed as the varied, likable cast, this simply-phrased time-travel fantasy will please fans of the genre. Meanwhile, the point about responsibility for unforeseen consequences of rash acts is gently but firmly delivered.