Host David Yetman joins his brother, geologist Dick Yetman, for an exploration of the traces of humans along the Colorado River and Grand Canyon region. They observe sacred salt mines from the boat, visit the intersection of the Little Colorado River with the main river and even enjoy an impromptu canyon concert. The brothers learn the history of rapids - how they got their names, the scales of intensity and spend time with scientists studying the effects of the Glen Canyon Dam on the flora and fauna of the Grand Canyon.