James Gordon, Sr., owner of the Gordon syndicate, dispatches his roughneck son Jimmy to investigate why production has fallen off in his opal mine on an island off the coast of lower California. After an argument with his fiancé, socialite Lucy Andrews, Jimmy leaves for the island where he is met by Juan, McCool's servant who, along with Jasper Sneedham, has been cheating the company. On the launch, Juan tries to eliminate Jimmy by hitting him over the head, but escapes and swims to shore where he is rescued by Sneedham's stepdaughter Nadine. Nadine takes Jimmy to the hut of mine foreman Fred Haimer, the only honest man on the island. When Nadine overhears her stepfather's plans to take his ill gained fortune and flee, Jimmy and Haimer team up to defeat Juan, Sneedham and McCool. After a number of grueling skirmishes, Jimmy, Haimer and Nadine escape to the mainland where they notify the police who return to the island and arrest the gang.