The Dragon's Jaws by Frank L. Packard

Roy Melville goes to China to save his kidnapped father, who is being held for a million-dollar ransom in diamonds. On the voyage over he meets Myrna Lang, whose father is murdered in mid-ocean, and learns from her that their tragedies have a common instigator—the evil, mysterious Lan Chao-tao, a Chinese star bandit, whom few have ever seen but whose appalling activities have spread octopuslike throughout the world. These two young people unite in a valiant effort to best their mysterious enemy, and the result is a story of breathless incidents which hinge on such unusual things as the action of tides in Chinese rivers, the architecture of a certain deserted temple or the anticipated actions of Chinese militia.