Biggles and the team investigate some strange rumours emanating from a supposedly deserted Pacific island.

With some help from the French and Swedish Police, Biggles uncovers a self-proclaimed king, seeking to develop a new master race (although from a dubious collection of breeding stock). Biggles thwarts those plans, leading all the captives to safety, avoiding a pack of ferocious dogs in the process. As it turns out, all just in time. The occasional earth tremor turned out to be the warm-up for the main event - a massive eruption that engulfs the island and the remnants of the king's command.