In a succession of distinguished books, Zilpha Keatley Snyder has been exploring the nature of magic, not only for the benefit of children, one feels, but to satisfy herself—which is, of course, how all good books are written. Invariably at the center of her magic is an oddball—a highly individual, nonconforming, compelling character, so inventive … as to suggest that magic lies within the power of imagination itself. (p. 8)

With each book the pattern of Mrs. Snyder's magic becomes clearer, more closely entwined with reality. In one sense, her characters are themselves the magicians. Unlike Alice, who emerges from her rabbit hole ready to take up childhood just where she left off, they are never quite the same after their adventures. And indeed, one asks, how can magic not leave a mark?

"The Witches of Worm" is one of Mrs. Snyder's most haunting stories and one of...