"the plains of passage" describes the journey of ayla and jondalar west along the great mother river (the danube), from the home of the mammoth hunters (roughly modern ukraine) to jondalar's homeland (close to les eyzies, dordogne, france). during this journey, ayla meets the various peoples who live along their line of march. these meetings, the attitudes and beliefs of these groups, and ayla's response form an essential part of the story.