Martha's Vineyard, 1650s: Bethia Mayfield is a young girl growing up in the tiny settlement of Great Harbor, amid a small band of pioneers and Puritans. Restless, bright and curious, but denied the education that her brothers receive, she slips away as often as she can to explore the island's wild landscapes and observe its native Wampanoag inhabitants. At the age of twelve, she encounters Caleb, the young son of a chieftain, and the children form a secret friendship that gradually draws each into the alien world of the other.

Meanwhile, Bethia's minister father is trying to convert the Wampanoag, awakening the wrath of the tribe's shaman against whose magic he must test his own beliefs. And when he takes it upon himself to educate Caleb, it will further divide the communities - within a year the boy is learning Latin and Greek, and leaves the island to study at Harvard. As Caleb makes the crossing into white culture, Bethia finds herself pulled in the opposite direction. Trapped by the narrow strictures of her faith and her gender, she seeks connections with Caleb's world that will challenge her beliefs and set her at odds with her community...