When Trixie was granted the position of Speed's assistant in the No Limit World Race, Inspector Detector and his officials search each entry, looking for $50,000,000 in stolen gold bars before the race begins. When the Mammoth Car enters the track, its driver gives the Inspector a tour, showing no trace of the gold. When the race begins, the Mammoth Car forces everyone off the road, making Speed a bit suspicious. On its way to discover the Mammoth Car's secret, he equips the homing robot with X-ray film so he can be able to penetrate the metal...