People and animals are dying mysteriously and in droves on various ocean shores, a catastrophe caused by high-frequency sound waves generated by the ruthless diamond-mining techniques of Australian tycoon Arthur Dorsett, whose fiendish plan is to ruin the diamond cartel and corner the colored gem market. Sometime after Pitt gets on the case, he winds up being cast adrift by Dorsett in a small, leaky boat in the Pacific; also on board are steadfast Al and Dorsett's rebel daughter, Maeve, who provides the novel's love interest. The three are shipwrecked but survive to build a small craft that will take them to Dorsett's island fortress, where they hope to rescue Maeve's twin sons, hostages of the unlikely villain (Dorsett suffocates one enemy by stuffing his mouth with diamonds). Meanwhile, Admiral Sandecker realizes that the deadly sound from Dorsett's four Pacific mines will soon converge in Honolulu, killing everyone there.