Speed resumes the Sword Mountain Race, neck and neck with Duggery. Ace and his gang approach from the opposite direction. Speed swerves off the road and uses his rotary saws to cut a path through the overgrown terrain. Trixie creates a temporary distraction, bombing the gang with smoke flares from her plane. At a cross-road, Duggery decides to take a "shortcut." Speed knows that the road leads to a dangerous volcano and sets out to rescue him.
Meanwhile, Ace and his gang fire at Trixie. The plane plummets but Trixie escapes. At the edge of the volcano, Duggery is thrown from his car, and left dangling from a rock. Speed also ends up on a rock shelf after trying to rescue his competitor. They manage to reach safety but find that the gang surrounds the Mach 5, with Trixie taken hostage.
Spritle and Chim Chim, who have hidden in the Mach 5's trunk, throw rocks at the gang while Speed, Duggery, and Trixie fight them off. Ace takes off in the Mach 5. Speed follows in hot pursuit.
父・大介の考案した新型エンジンの開発資金を稼ぐため、剛は大介に隠れて剣山トライアルレースへ出場。しかし、マッハ号の風防ガラスに隠された新型エンジンの設計図を狙い、悪漢ブラック一味が襲い掛かる。
