Cussler's hero, Dirk Pitt, appearing for the thirteenth time, leads a National Underwater and Marine Agency expedition to discover why seals and dolphins have been disappearing on Seymour Island in the Antarctica. But the novel actually begins in 1859, when a British ship carrying convicts to Australia sinks. Eight survivors reach land, a deserted island. In the year 2000, naturalist Maeve Fletcher, one of the descendants of two of the survivors who'd married, is stranded on Seymour Island with passengers of a cruise ship and is rescued by Pitt. From here, the plot gets implausible; Pitt discovers the cause of the plague that's killing the sea life, an ultrasound resonance that produces acoustic shock waves under the water. Maeve's father is the villain; sound waves are part of his diamond-mining technology, and the next big blast could kill a million people. It's up to Pitt to stop him, of course.