A flash of lightning, quivering ground, and, instead of her grandparents' farm, Polly sees mist and jagged mountains -- and coming toward her, a group of young men carrying spears.

For this time-slip novel, L'Engle again reaches into her bag of weird and wonderful knowledge, blending snippets of tantalizing information from a variety of disciplines--history, natural history, physics and Christian metaphysics, to name a few--into a rich and heady brew. Red-haired Polly O'Keefe arrives at her grandparents' farm in Connecticut for some private tutoring. There, in a landscape familiar to L'Engle fans, Polly slips back 3000 years into a different time "spiral." She meets Anaral, a Native American girl; Karralys, a druid banished from Britain for his progressive thinking; and Tav, a handsome warrior who accompanied the druid to their new land.

Polly travels back and forth between the two worlds, and eventually her purpose becomes clear: with the aid of her new friends she forges peace between two clashing tribes, and helps Zachary Gray (also from A House Like a Lotus ), a self-centered but very ill young man. The story is laced together with L'Engle's now-familiar theme of the transcendent importance of love. This fine fantasy, firmly rooted in reality, is the kind of thoughtful story at which L'Engle excels.