While out on a practice race, Speed is almost run off the track by a mysterious black car. Later that night, the black car gains on an automobile whose driver recognizes it as the X3. Before causing the auto to crash, the black car broadcasts, "Melange still races." A second car is also caused to crash. The next day, Inspector Detector asks for Speed's help. While Spritle and Chim Chim hide in the Mach 5's trunk with a tape recorder, a chase ensues, but the X3 outdistances Speed. Spritle produces a tape recording of the X3's message. Pops explains that the recent victims were the coaches of the Three Roses Club race team, the expected victors of the Danger Pass Race. However, they were worried Slash Market driving car number X3, the Melange, might beat them. Mysteriously, the Melange crashed. Pops recalls that Slash had two children – Slash Jr. and Lilly. The Inspector, Speed, and Trixie pay the siblings a visit and learn that they know nothing.
Elenco: Katsuji Mori , Teiji Ōmiya , Ryoko Kinomiya , Junko Hori , Kei Tomiyama , Kenji Utsumi , Hiroshi Ohtake , Kin'ya Aikawa , Michiko Nomura .