The episode once again involves a conspiracy to assassinate Emperor Rudolph, this time by Prozen-loyalist generals in the Imperial military. Although the operation's leaders are apprehended by Van, Thomas and the Guardian Force, the assassin decides to act anyway, and promises to kill Rudolph at the upcoming Guylos Grand Prix event. Van and Thomas discuss the assassin, who calls himself "Phantom", with Rosso and Viola. Viola mentions that the Prozen-loyalists evidently wanted to use the enormous media attention attracted by the Grand Prix to their advantage. Rosso is concerned that Phantom may be "a slippery one", but Van is confident that the assassination will not be able to get past the Guardian Force.
Moonbay enters the Grand Prix, with Irvine and Dr. D acting as her support crew. It turns out she used to race four years ago, and has only just returned to racing. She ranks first, although a mysterious rookie, "Masquerade", a masked racer, tails her on her laps. Even with Fiona and Zeke as his bodyguards, and with over three hundred men protecting Rudolph, Van is concerned and decides to keep on the lookout. Phantom takes to the seas, using a customized Gun Sniper and a stealth boat, and starts taking practice shots at a floating target. Rudolph is resolute in his determination to attend the race, and Van and Thomas continue to survey the area, trying to find the vantage point from which the Phantom will be sniping.
The next day, the race begins and Moonbay almost stalls off the blocks, even though she's using an engine "liberated" from the military by Dr. D. The masked Masquerade, right behind Moonbay, is also held back by this. Moonbay recovers as Van and Thomas continue their search. Phantom sits and waits for Rudolph to stand in the right spot, as his line of sight is very, very narrow. After a tipoff from a fisherman who saw the Phantom turn on his stealth, Van and Thomas use heat sensors to find the boat and shoot at, but it self-destructs and the Phantom escapes underwater.
Van notices him walking in a crew-worker's clothes, and moves to intercept him. Meanwhile, Moonbay moves to first, with "Masquerade" right behind. Masquerade tries to overtake Moonbay, who catches her Sinker on the net and is left in a neck-in-neck race. Moonbay's engine gives out and Masquerade wins the race. Just then, Phantom sets off some bombs in the Gustav hanger, luring out Rosso and Viola, who he distracts with a smoke bomb. However, as he takes the shot at Rudolf, his bullet travels straight though him- it was a hologram all along, Rudolph was actually the masked racer, and Van arrests him.
Meanwhile, Dr. D frames Irvine and Moonbay for stealing the engine he "borrowed", and gets them arrested.
- Moonbay was known as the "legendary fireball" in her past racing career.
- The Phantom is implied to have been in possession of his Gun Sniper for a long time, despite it being declared a new Zoid in episode 2.
See also: Zoids: Guardian Force