Race For Revenge (Part 1)
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.
Aired 28/10/1967EP 12 - Race For Revenge (Part 1)

Speed Racer
The Mach 5 is one of the fastest and most technologically advanced race cars built by man. Equipped with various gadgets and a powerful engine, it provides a challenge for anyone who would dare race against it. The driver of this amazing vehicle is Gou Mifune, a teenager who dreams of breaking into the world of professional racing.
In spite of this, Gou's father and the creator of the Mach 5, Daisuke Mifune, does not want his son anywhere near a racetrack. Undeterred, his girlfriend Michi, younger brother Kurio, and Kurio's monkey sidekick Sanpei become Gou's biggest fans as he sets out to become the greatest racer of all time.
However, Gou soon learns that becoming a professional racer is not easy. From the underhanded plots of corrupt businessmen to stiff competition in the form of his rival, Racer X, Gou faces many obstacles on the road ahead, and has a lot to prove before he can cross the finish line.
(Source: MAL Rewrite)