William "Wild Bill" Dunn is an American engineer working with the army in a secluded section of Ethiopia. While working, his team is attacked by a group of supernatural beings named the M'bujies. The M'bujies wound Dunn and kill his teammates. Dunn is rescued by "Boomerang" Jones, an Australian soldier who had been given up for dead and is now fighting his own private war against the Nazis. After Dunn regains his strength, the two men create a super-vehicle out of captured Nazi equipment that they name the Blue Tracer. It can become a tank, airplane, or submarine. They then use it to destroy the M'bujies and escape the jungle. The two travel the world and fight the Axis forces during the rest of the war, with Dunn at the head and Jones as his sidekick.