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.
Flash Bandeira Jr. tenta se vingar dos integrantes da Equipe 3 Rosas, que participou do complô contra seu pai causando sua morte. Para tanto, Flash traz de volta Mellage, o carro que seu falecido pai projetou. Controlando o automóvel a distância e usando sua irmã Lilly, disfarçada de piloto, o obcecado rapazbusca sua vingança. Speed arriaca sua própria vida para evitar uma tragédia na Corrida do Desfiladeiro do Perigo.
レース界の顧問と言われる緑川がグレーのスポーツカーに殺され、その現場には「X3」と紙に書かれた謎のメッセージが残されていた。剛は六郷警部に依頼され、犯人の車を追跡するが見失ってしまう。
