When Tommy How, a young chap, and a strange man named Kelso, arrive at Thunder River in need of a low-priced guide, Dave Sherman volunteers for the position. The three set out down the rough river on a makeshift craft powered by an outboard. When Kelso abuses Hank the Hermit's highly valued rock collection-- Dave decides to quit, but Kelso breaks his partnership with Tommy and goes off with another guide. Tommy and Dave, with the help of Hank and Ben, the man with whom Dave lived for years, search diligently for a jade ledge discovered by Tommy's Chinese grandfather. Sabotage, a forest fire and the river itself increase the suspense; the build up is more exciting than the climax itself. Pure adventure adequately written by the author of The Secret of the Himalayas (1962, p. 573, J-171).