

At the racetrack, the Stunt Car Spectacular promises "action and thrills." Two contestants attempt to scale a ramp and clear a stack of cars, but fail. Daredevil driver (and member of the Car Acrobatic Team) Snake Oiler urges Speed to try. Speed, instead, challenges Snake to the upcoming Big Alpine Race. Later, Speed and Pops head toward a difficult section of the course where each driver must leap over a deep cavern without plunging into the river 1,000 feet below. At the site, the Car Acrobatic Teams demonstrates their remarkable ability, twirling in the air over the cavern. Before Speed's attempt, Racer X offers advice. At Pops' garage, Pops wishes he knew the secret behind the abilities of the Car Acrobatic automobiles. Spritle and Chim Chim overhear this and sneak away at night to spy on the team. Spritle returns with photographs detailing the special devices that make the cars fly. Before long, the Mach 5 is outfitted with wings. Pops passes out from exhaustion.
After winning a practice race, Speed Racer is offered a position on a team set to race in the Grand Prix. The company who employs his father, Pops Racer, a top engineer, owns the team. However, Speed declines because Pops doesn't want him to become a pro. Meanwhile, Pops quits when his plans to improve the Mach 5 are rejected. While Pops and Speed are driving home, a gang of motorcycle racers steals their plans. Trixie, in her helicopter, runs the gang off the road and the plans are recovered. Back at the cyclist headquarters, bad guy Acey Ducey shows up and offers to get the plans for "5,000 clams." He confronts Pops but leaves empty-handed as Pops has hidden the designs on the Mach 5's windshield using invisible ink. Deciding to sell the Mach 5 so Pops can rebuild the engine, Speed visits Sparky, who suggests that Speed enter the Sword Mountain Race for a $5,000 prize. While Speed takes the Mach 5 out for a road test, "dirty driver" Duggery rams the car, causing it to blow a tire.
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.