Challenger develops a new way to create lift in the balloon. All go along for a test flight, but the balloon is drawn into violent turbulence then crash-lands inside the vast caldera of an extinct volcano where our heroes find themselves trapped in a world beneath the earth's surface. With the balloon damaged and the supply of iron lost, our heroes can only survive for a matter of days in this hot and hostile environment.

Aleece, a strong-willed female warrior-in-training, hurries to the rescue. In exchange for a ride in the balloon she offers to help replenish the iron that is needed. Malone accompanies her to a mine, but instead of raw ore, her plan is to steal from the supply of a vengeful exile named Arjax. After being caught by Arjax, Malone and Aleece face death unless they lead Arjax back to the balloon.