 Dr. Reynold and Prof. Ogden are suddenly attacked by a tribe whose members are wearing a distinctive blue face paint, something neither of the men has ever seen before. The attackers are driven off, but Reynolds and Ogden manage to wound and capture one of the warriors. While the native recovers from his injuries, Tom, Howard and Charlie set out to discover what caused the unprovoked attack, and find out the meaning of the mysterious blue face paint.