Trixie wins the position of Speed's assistant in the No Limit World Race. Before the race begins Inspector Detector and his officials search each entry looking for $50 million in stolen gold bars. The Mammoth Car enters the track. Cruncher Block gives the Inspector a tour, yielding no trace of the gold.
The race begins. The Mammoth Car forces everyone off the road. Speed is suspicious. To discover the Mammoth Car's secret, he equips the homing robot with X-ray film able to penetrate metal. Unfortunately, it's shot down and returns broken. The Mammoth Car catches up to Speed and forces the Mach 5 off the road. A ramp is lowered and a squad of motorcyclists descends onto the track. Racer X appears and spritzes oil on the road, causing the cyclists to crash.
Meanwhile, at the airport, Spritle and Chim Chim stow away aboard Cruncher Block's plane. Back on the track, the Mach 5 and the Mammoth Car collide and both veer off the road toward a forest.
A mais célebre das aventuras de Speed Racer, onde o piloto terá de usar todos os equipamentos do Mach 5 para vencer a Corrida Mundial Sem Limites e impedir que o gigantesco Carro Mamute cruze a fronteira com 50 milhões em ouro roubado.
金塊強奪事件を追う六郷警部は、本土縦断ロードレースに犯人が紛れ込んでいると推測する。そして警部がにらんだ通り、レースに参加する巨大トレーラー・マンモスカーに犯人一味が乗り込んでいた。
