Ling Ling's estranged sister, Lang Lang, shows up at the Narutaki Detective agency unexpectedly. Six months prior, she had joined with Narutaki's rival, Le Bled, and ran away with him. Now, Le Bled has come for a showdown with Narutaki, and Lang Lang's visit is part of his plan. Lang Lang gasses Ling Ling and disguises herself as her sister, then tries to poison Narutaki. He, of course, is too smart for all that. When the plan is foiled, Le Bled appears, and tells Narutaki the only way to save Ling Ling is to defeat him in battle. The fight is joined, and Narutaki does save Ling Ling, but in doing so, Lang Lang and Le Bled are able to escape.

The Crimson Scorpion is on a thieving rampage! She is using disguises fluidly and stealing all sorts of jewelry, but she keeps being disrupted by Narutaki and she ends up getting away with nothing. However, the Crimson Scorpion has set her sights on the most important piece of the Kebecks Royal Jewels – the Blue Teardrop. This necklace is worn around the neck of the reigning female royalty, and the Royal Princess of Kebecks is going to be wearing it during a ceremony when her engagement to the Steam City Prince is announced. Can Narutaki stop this criminal from stealing this important piece of jewelry?

As Knight Phantoms reign of terror continues, Steam City has been evacuated and the city is a mere ghost town in the wake of his devastation. It's going to be Narutaki's most intense battle yet, but with so many people caring about their beloved Steam City, even enemies may be willing to lend a helping hand.