This is the Oz book which L. Frank Baum considered his best. It starts quietly enough with Trot and Cap'n Bill rowing along a shore of the Pacific Ocean to visit one of the many caves near their home on the California coast. Suddenly, a mighty whirlpool engulfs them. The old sailorman and the little girl are miraculously saved and regain consciousness to find themselves in a sea cavern. To this day, Trot asserts she felt mermaid arms about her during those terrible moments under water. From here on, one perilous adventure crowds in upon another.