Ash and friends are lost while on the trip to Solaceon Town. They find a mansion nearby and decide to check it out. When they approach, they are attacked by a young girl named Marble, her Luxray, and a bunch of security guards, who believe they are thieves. The owner comes out and the misunderstanding is resolved. The owner, Matthew, reveals that three criminals want to steal his treasure, the Old Charm, at eight o'clock. It turns out that Team Rocket are the thieves and they make off with the treasure. Their plan ends abruptly when their balloon pops and crash lands in another part of the mansion. Everyone heads to get there, but Team Rocket falls prey to the mansion's traps. Now it is up to Ash, Dawn, Brock and Marble to find Team Rocket and get the Old Charm back, but with a mansion full of traps and a disobedient Luxray, that may be harder than planned.
Dawn and Ash believe they got lost, but Brock knows past the forest is a town. However, they encounter a mansion. They go to ask the owners to sleep for the night and get spotted by a woman, though her Pokémon attacks them, causing ruckus. Pikachu hides, but the Pokémon has a sharp vision and attacks the shrub, though Pikachu evades. Luxray disobeys her mistress and collides with Pikachu using Iron Tail. The guards come to arrest them, but get electrocuted by Pikachu's Thunderbolt. The woman is delightened by such attack, but still accuses them of being bandits. A man comes and recognizes them as participants of Hearthome City's Tag Battle Tournament. The heroes introduce themselves, while the man is Matthew and the woman Marble. The bandits wanted the Old Charm, as he received a note they plan to steal it.
He asked Officer Jenny for help, making Brock happy for that fact. So, Marble came to investigate the matter. Dawn questions her capabilities, but the man thinks they could help her. Marble agrees, though they need to work under her commands. Pikachu spots Luxray does not like him, after everything has been cleared up. Marble knows that somewhere around 8 o' clock should the thieves come, though Marble is concerned about Luxray - when it evolved, it couldn't learn any new Electric-type moves. When she tried to catch a thief, Luxray couldn't use any electric moves, so the Arcanine got the thief. Since then, Luxray wouldn't hear her commands.
Luxray did not like Pikachu because he is able to use Electric-type moves. She believes that with some training, it can learn some moves and it will be under her command once more, but this could get Luxray very, very angry. Team Rocket came and are disguised as policemen. Team Rocket has a fantasy what the treasure might be, so they go to get it. Team Rocket tells them they got orders to move the treasure, so Marble and Brock agree, as it might be well enough to fool the bandits. Dawn thinks they are thieves, but the doubt is removed, as Brock thinks the clock must have set back. Matthew comes and is surprised to hear that he ordered to move the treasure, which he didn't.
Team Rocket blows the wall and goes on the balloon. Pikachu goes to use Thunderbolt, but Luxray pushes him away and goes to use Iron Tail, but is punched by the robot arm. Ash sends Staravia, who uses Quick Attack. Still, Team Rocket's balloon moves away, dodging the attack, but the balloon is cut on a roof spike. Team Rocket goes out and on a press on a plate, they activate the trap and fall down. The heroes see they are gone and believe they went through the hall. Matthew warns them there are series of traps lying around. Luxray sees this with the vision and jumps, pushing Pikachu on the platform. Luxray goes to get him, but they fall down. The heroes ask if Matthew knows where the trap leads, so Matthew shows them the way. Pikachu and Luxray see many series of possible exits, even if Luxray still does not want cooperation.
The heroes see the way through the fireplace. Marble promises to get the treasure back for Matthew. Luxray charges and almost falls down in the trap with spikes, but Pikachu pulls it up... barely. With this, Luxray begins to cooperate. Marble knows Pikachu and Ash are a good combination, but he confesses that it was rough at the beginning, but managed to get on well. Ash does not know how Luxray should obey her, but knows he and Pikachu are friends. Marble knows she was too afraid to be Luxray's friend and thanks him for advice. Since there is no exit, Team Rocket digs a tunnel to get out. Luxray uses its vision to see the exit. It opens one and Pikachu runs, but triggers a trap. Spikes come out, but are deflected by Luxray's Iron Tail. The heroes came and re-unite with Luxray and Pikachu.
Marble asks Luxray if they can be friends and Luxray confirms this. Jumping of joy, Marble triggers a trap and the walls are moving to squish them. Brock knows there must be a switch, so Luxray searches and uses Iron Tail and pushes the switch. The walls go back before anyone is squished. Team Rocket dug out the tunnel, but to the heroes. Meowth opens the box and sees it is not gold, but a shiny amulet, so he stores it in another box. Jessie sends Seviper and James his Carnivine. Seviper goes to use Poison Tail and Carnivine goes to bite, but get canceled by Luxray's Iron Tail. Pikachu electrocutes them and Luxray jumps and stores electricity. With Charge Beam, Team Rocket drops the box with the Old Charm and Dawn catches the box. With a Thunderbolt and Charge Beam, Team Rocket is blasted off.
Matthew knows the box is locked, but with Luxray's Thunder Fang, the box opens. Marble is now happy she solved the case, though Jenny is not impressed, as she did not ask. Brock, naturally, flirts with her and gets stabbed by Croagunk. Jenny apologizes to Matthew if Marble caused trouble, but Matthew responds she was helpful, causing her to thank Marble and Luxray. Matthew offers them breakfast. Ash knows he can eat more than that and Dawn wanted to say the same, stealing Marble's line.
This is the final episode where Dawn's Piplup doesn't appear.
In one scene, Marble's suit also covers her right shoulder, while her shoulder is supposed to be uncovered.