After falling asleep in a park, fourteen-year old Zan awakens to find herself transported back in time to the forest world of a band of prehistoric cave dwellers. Adopted by the group, she learns their language and customs, exults in their triumphs, and shares in their grief. However, the society's wise woman has her doubts about Zan, who she believes has brought misfortune with her. In mortal danger, Zane is able to return to her own time—an eleven-month absence which was only a few hours back home.

Norma Fox Mazer (1931–2009) was an American author and teacher best known for her books for young adults. Among the honors Mazer earned for her writing were a National Book Award nomination, a Lewis Carroll Shelf Award (for Saturday, The Twelfth of October), and a Newbery Medal.