The Streets here are continually enshrouded in white mist. Steam rises from everywhere, obscuring the streets and buildings. Because coal was the only fuel available, this city developed an incredibly advanced steam technology. Unfortunately, evil-doers take advantage of this white fog to commit countless crimes and continually baffle the police. At night, the white mist shrouds the darkness, intimidating everyone. People Call this city enveloped in mist, STEAM CITY.
A new criminal has begun operating in the steamy shroud that covers Steam City. The city police cannot keep up with him- he claims that his megamaton has teleport abilities, and it seems to be true. Whenever the cops get close, the machine vanishes in a mysterious fog. Enter the Narutaki Detective Agency. Child sleuth Narutaki hits the set, and quickly gets a hunch regarding the "teleporting" mecha. While the police chase shadows, Narutaki finds the real villain, and the battle is on. After Narutaki's megamaton, Goriki, defeats the enemy machine, the criminal reveals himself- he is Knight Phantom. He speaks of his hatred for Narutaki, and vows to destroy everything he loves. But Narutaki doesn't seem to know who this stranger is.
On his way home, Narutaki sees a young girl kidnapped. He pursues, and eventually frees the girl. When her father comes to get her, they learn that he is a scientist, working on a powerful new power source that could do away with steam energy forever. The assumption is made, that Gina was taken to trade for her father's research. Soon, the girl is taken again, and this time a ransom demand is made- the kidnappers indeed want the meteronite, the crystal energy source her father is developing. A trade off is setup, but at the last minute, Narutaki realizes it is a double cross- Gina's live in tutor is actually the Crimson Scorpion, a thief desiring all beautiful things for herself.
The Machine Baron- The Ultimate Collector. He desires unique and antique machines, old robots, vacuum cleaners, watches; anything of witch there is only one in the world. The villain crashes an antique machine show, but is handily defeated by Narutaki and Goriki. He vows his vengeance, and in order to learn Goriki's weaknesses, disguises himself as a reporter, wanting a story on Narutaki. As time passes, the Machine Baron's desire to destroy Goriki turns into a desire to possess the machine. Unable to bring himself to destroy Goriki when he has the chance, the Machine Baron must finally admit the truth- he has fallen in love with Goriki!
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.
A major convention of world-renowned scientists is coming to Steam City, but there is a problem- someone has been kidnapping the attendees. Narutaki narrows down the list of potential targets to the next two, and goes to warn them. Later, one of them is indeed snatched, but Narutaki and Goriki foil the attempt. Later, at the convention, it is revealed that the other, Dr. Gerhalt Von Halt, is the one behind the kidnappings. He wants the knowledge of the scientists to make his megamaton better than human. He claims his evil identity- Dr. Guilty- and tries to capture the remaining scientists. Narutaki is having none of it, however, and the battle is on. Dr. Guilty's megamaton is strong, however, and Goriki is badly damaged. Just when it seems as though the heroes will be defeated, the scientist Narutaki saved earlier gives Narutaki special bullets; with which the bad guys are at last defeated.
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?
Narutaki's good nature becomes his downfall as he escorts a scared young lady home and is subsequently gassed and knocked out. During the night, a local bank is robbed by a megamaton that looks like Goriki. When Narutaki wakes up, he makes his way home only to have the chief detective of the police waiting for him… they want to arrest Narutaki and remove Goriki's coal. How is Narutaki going to prove their innocence?
The mastermind villain Le Bled shows up at Narutaki's home and suggests a competition: if Narutaki can find the 3 great treasures of Steam City in an 18 hour period, Le Bled offers to surrender to police, but if he cannot, Narutaki agrees to stay out of Le Bled's affairs. The competition becomes even more intense once Narutaki discovers that the treasures are in fact bombs and are set to go off at the deadline...
Narutaki meets with a scientist associate whom he helped earlier. Apparently scientists in the field of energy research have been disappearing then reappearing for a few days at a time. Narutaki starts to do some ground work on this mystery until Ling-Ling is attacked while trying to stop a masked man from kidnapping two prominent scientists. The masked man is the Phantom… and he made off with the scientists, but not before Ling-Ling managed to put a tracer on him. Will Narutaki face this foe?
In Steam City's coal mine, an excavation was stopped due to a cave in. However, one of the miners believes that the cave in was caused by a giant mole creature. Narutaki joins the local police on the site, and another mineshaft comes across a new cavern that has been recently dug. Narutaki takes Goriki with him, and while in the cavern, they come across Dr. Guilty's latest creation: Shadowbolt Mark II. After a quick fight, Shadowbolt II escapes, but our heroes are caught up in a cave-in. Making matters worse, Dr. Guilty brings his creation downtown and begins tearing up the city. Will our heroes escape the cave-in and will they be able to fight?
There's a festival approaching to celebrate the dragon guardians of Steam City, but to everyone's surprise, a real dragon shows up and begins breaking into the local jewelry stores. At least, it seems to be a real dragon. The shop owners are living in a state of perpetual terror, and it seems that only Narutaki will be able to crack the case.
The devious Machine Baron arrives on the scene, but his latest scheme has a major flaw in it. It seems that the robot he intends on unleashing upon the city has lost its power source, and while he searches the city, and buys himself some time, Ling Ling finds the device and, thinking that it's an old fashioned sauna, takes it home to help with her latest diet.
Narutaki has to deal with his toughest case yet. Ling Ling is made at him, very mad, and the two aren't even on speaking terms. He might have another case in his lap searching for a missing cat, but that's going to be easy compared to overcoming Ling Ling's attitude.
King Steam, a character straight from a horror novelists books shows up in Steam City, and stopping him isn't going to be easy. The mystery isn't how to stop him necessarily, but is it a fan imitating art, or is it the creator himself bringing his horrendous creations to life?
Someone's got an eye out for Onigawara, or at least that's what it seems. A beauty that he bumps into that's fleeing from a pair of goons moves into his building, and seems to really be smitten by him, but Narutaki thinks differently, and fears that she may be trying to pull the wool over his eyes.
Lang Lang is back, but she's not trying to mend her ways or patch things up with her sister. She has met a young girl who is about to undergo a dangerous operation that might be her last and, feeling sympathetic to her plight, she and La Bled manage to halt the procedure from taking place in order for her to grant the girl on special wish.
When an experimental submarine shows up in Steam City's rivers, it seems like no one can stop it, and that's just the way that Knight Phantom wants it. He's managed to get his hands on one of the Navy's pride and joys, and they'd just as soon keep it under wraps than allow Narutaki and his detective friends get their hands on the truth.
This episode takes a look back at some of the more memorable cases from those that know them best in Steam City.
The Crimson Scorpion is on the prowl again, and although her original target is a very valuable gem, she switches plans and goes after something unexpected. Nanutaki knows about the crime that she is about to enact, but even to his surprise, she's stolen a sword that everyone thinks has no value at all.
Recently, detective all over have been disappearing, and Ling Ling fears that Narutaki may be the next in line. Her fears are correct, and the vigilante called Justice comes to Steam City with but a single goal in mind: to eliminate the worlds detectives, and Narutaki is the next target. In order to keep him safe, an escort is brought onboard to keep an eye out, but Justice may be closer than anyone ever imagined.
La Bled is on the move again, but this time he leaves behind a clue that reveals something very disturbing. After careful research, Narutaki has discovered that his rival is dying, and it seems that he may have struck up an alliance with a well-known producer, but the reasons are unknown. However, it seems that La Bled has something very special planned for Narutaki, but he's going to have to attend a special performance of the play . . . alone.
The curtain rises, and Narautaki finally witnesses what La Bled has put together. However, in order to keep the young detective in line, La Bled has a gun trained on him, and should he leave his seat, the gun will go off. The play however doesn't seem to be a trap at all, but instead a reflection of the life of a dying man.
What should be a simple and routine shopping trip for Ling Ling turns into much more when she crosses paths with Dr. Guilty. Although he's been injured running from the police, he still has the energy to kidnap her and steal her car. But when the police and Narutaki finally catch up to him, Guilty has another plan, and it's going to bring a very familiar face into the world of crime, temporarily at least.
With the incident involving Dr. Guilty behind them, things slowly go from bad to worse. Goriki, who was badly damaged, looks as though he is beyond repairs, and everyone that Narutaki has any type of association with seems to be victimized by mysterious circumstance. Then, Ling Ling is kidnapped again, and it's Knight Phantom that surfaces as the one behind the chaos, and he's got an even bigger and potentially deadly plan.
Everything is falling apart, and Narutaki is desperate to find out what Knight Phantom's goal really is. He soon discovers that 13 years prior, Knight Phantom's father was killed, and as he boldly states, by Narutaki's parents. It seems however there may be something else that is more sinister hiding in the shadows of the past though, and Narutaki attempts to uncover the truth.
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.