Thunder in the Sky (First Americans Saga);

The grassy Great Plains shake with thunder and deadly tornadoes whirl down from storm clouds as the First Americans begin the battle the will determine which peoples--the savage or the gentle--will shape the future or humankind.  On one side is the young shaman Cha-kwena, who has led his tiny band along the trail made by a magnificent white mammoth, the totem he believes will lead the People to a land of safety and abundance.  But they are pursued by enemies, a race of vicious and relentless hunters who want to steal Cha-kwena's magic, kill his sacred mammoth, and possess his passionate woman.