Brother and sister Casey and Kiley go back in time again. In this adventure, they travel back in time to North America before it was discovered by European explorers. They face fierce, wild animals and help a Native American boy who is injured. History comes alive as they explore a world without pollution, learn about Native American culture, and learn the origins of lacrosse. The two children work together as a team, show respect for the environment, and do the right thing despite the dangers.