Ash and co. are walking in the forest towards the next town. Ash and Dawn suspect that they may be lost, but Brock is confident that the next town is just beyond the forest. Up ahead, the group sees a huge castle. Even though it is not the town they were looking for, Ash thinks that it would be wise to stay there for the night. While Ash and co. are walking closer to the castle, they notice that there is no one around. Suddenly, a bright light shines are the group. A girl and her Luxray stand on the roof of the castle. She thinks that Ash and co. are bandits. Luxray jumps from the roof and attacks Pikachu. Pikachu tries to avoid Luxray by hiding in he bushes, but Luxray is able to sense Pikachu's location. Dawn looks up Luxray in her Pokédex and discovers that Luxray can see through anything. Suddenly, Luxray's trainer appears. She notices that Pikachu is a powerful Pokémon. Several guards surround the group, but Pikachu blasts them away with Thunderbolt.
The battle ends, and Ash and co. tells the girl that they are not bandits. The girl doesn't believe them. However, a man named Matthew walks out and states that he has seen Ash and co. on TV before from the Hearthome City battle. Ash and co. agree and introduce themselves to the girl and Matthew. Then they ask who the bandits are. Matthew explains that the castle contains a valuable charm, and that he received a letter from a few bandits who stated that they planned to steal it. Matthew also says that he has to take extreme caution to protect his treasure, so he asked Officer Jenny to help. Then the girl introduces herself as Marvel, the number one detective who plans to solve the mystery. Matthew thinks that it would be a great idea if Ash and co. could help solve the case. Marvel is okay with the idea as long as she is the boss of them.
Ash and co. finally arrive inside the castle. The treasure is contained in a room. On the letter, the bandits stated that they would steal the treasure at 8:00PM. They look at the clock and find out that it is only 7:30PM. Dawn says that all they have to do is stand guard. Marvel explains that the process is not easy. Her Luxray has only recently evolved, and since then her Luxray hasn't been able to use electric-type moves. The situation only got worse when they were unable to stop a thief. After that, Luxray doesn't even listen to Marvel anymore. Dawn now understands why Marvel was impressed with Pikachu's moves. If Luxray could learn the electric-type moves, then it might start listening to its trainer again. Ash thinks that they should get down to training Luxray. Marvel tells Ash that training isn't easy because Luxray can get really scary when it's in a bad mood.
Meanwhile, Team Rocket is disguised in police uniforms. They approach the castle. Team Rocket is the bandits that everyone is looking for, but because they are in their disguises, no one notices them. Team Rocket wonders what exactly the treasure could be. Whatever it may be, they assume that it will give them wealth. Team Rocket peeks into the castle, and they see Ash and co. there. Team Rocket gets a little nervous, but Jessie reassures her partners that Ash and co. won't notice them. Team Rocket walks in and states that they have orders from Matthew to transport the treasure into a different room. Brock thinks that it is a good idea because it may confuse the bandits. Marvel agrees, so she allows Team Rocket to take the treasure. However, before Team Rocket can leave with the treasure, Dawn stops them. She wonders if the guards are the bandits in disguise. Marvel was thinking the same thing too. Suddenly, Matthew walks into the room and asks if everything is okay. Brock tells Matthew that the guards were just transporting the treasure like he ordered. Matthew doesn't recall saying that, and Team Rocket knows that they have been caught.
James takes out a remote and presses a button. Team Rocket's balloon bursts into the castle. The trio of thieves quickly jump into their balloon and say their motto. Ash and co. realize that Team Rocket was the real bandits. Ash orders Pikachu to use Thunderbolt. Before Pikachu can use the attack, Luxray pushes Pikachu to the side and uses Iron Tail. A mechanical arm is launched from the balloon, and it hits Luxray. Marvel notices that Team Rocket is getting away. Ash sends out Staravia and orders it to use Quick Attack. Team Rocket evades Staravia's attack. Suddenly, the balloon knocks into a sharp pin on the castle. The balloon pops and Team Rocket crashes to the ground. Ash and co. run towards Team Rocket.
Team Rocket recovers from their disaster. They begin to walk inside the castle. Suddenly, Meowth steps on a switch that is hidden in the floor. The switch triggers a trap door, and Team Rocket falls in it. Just after Team Rocket disappears, Ash and co. find their balloon. Ash and co. wonder where Team Rocket could have gone. Because there were no reports of anyone leaving the castle, the group assumes that Team Rocket is still inside. They decide to check the hallway. Matthew, however, warns the group that there are a number of booby traps lying around. Luxray immediately spots one behind Pikachu. It grows at Pikachu. Pikachu jerks backwards and accidentally hits the same switch Meowth hit before. Pikachu begins to fall into the hole. Luxray tries to save Pikachu, but it ends up falling too. Dawn wonders if Team Rocket might have also fallen down. Brock asks Matthew if he knows where the trap door leads to. Matthew states that there is a secret tunnel, and he leads the group to it.
Matthew leads the group towards a fireplace. He presses a secret switch and the fireplace opens, revealing a secret staircase. Matthew tells Ash and co. that the staircase leads straight to the pit, the place where Pikachu and Luxray went. Marvel promises Matthew that she will recover the stolen treasure back from Team Rocket. Meanwhile, Luxray and Pikachu are walking through the tunnel. Luxray suddenly walks on a secret switch. The floor drops and Luxray begins to fall. Pikachu quickly grabs onto Luxray's fall before it can fall in a pit of spikes. With all of its strength, Pikachu pulls Luxray back up to safety. Luxray is grateful and is able to trust Pikachu.
Ash and co. continue to walk down the staircase. Marvel is a little jealous of Ash because him and Pikachu get along very well. Ash explains that when he first got Pikachu, times were rough. After awhile, he became great friends with Pikachu. Marvel knows that she hasn't been good friends with Luxray. In fact, she has recently been scared of Luxray. Meanwhile, Team Rocket is busy digging their way out of the underground tunnel since they can't seem to find a way out by themselves. Pikachu and Luxray continue down the tunnel. Luxray uses its eyes to find a secret switch. It presses the switch and a secret door is revealed. The two Pokémon walk inside. Suddenly, Pikachu steps on another switch. Several spikes shoot out towards Pikachu, but luckily Luxray was able to break them with its Iron Tail just in time. Suddenly, another door opens and Ash and co. are revealed. They manage to find Luxray and Pikachu. Ash and Pikachu reunite with each other. Marvel walks up to Luxray and asks if they can be friends. Luxray finally accepts Marvel. Marvel is glad that she and Luxray are together again.
However, in Marvel's excitement, she accidentally steps on a secret switch. Both exits close and the two walls begin to close in on the group. If Ash and co. don't do something fast, they'll be crushed. Brock knows that there must be a secret switch hidden to stop the moving walls. Luxray looks around and finds one. It quickly presses the button, and the walls begin moving to the opposite direction. Suddenly, Team Rocket walks in. Their digging has led them straight into the room Ash and co. are in. Team Rocket notices this. Meowth opens the treasure, takes the item, and stashes it into the Team Rocket Super Secured Safe. Then Jessie sends out Seviper, and James sends out Carnivine. Luxray attacks the two Pokémon with its Iron Tail. Then Pikachu uses Thunderbolt on them. While Team Rocket's Pokémon are being blasted with electricity, Luxray tackles them. Luxray is now all charged up with electricity. Brock thinks that Luxray may now be able to use electric attacks. Marvel orders Luxray to use Charge Beam. Luxray is able to use the attack, and it blasts Team Rocket's Pokémon back at Team Rocket. The treasure falls out of Team Rocket's hands, and Dawn grabs it. To finish Team Rocket off, Pikachu uses Thunderbolt, and Luxray uses Charge Beam. Team Rocket blasts off again.
Ash and co. make it out of the underground tunnel. They give Team Rocket's case to Matthew. Matthew notices that the case won't be easy to open. So, Marvel tells Luxray to use Thunder Fang. Luxray bites on the case, and it finally opens. The secret treasure is revealed, and Matthew thanks Marvel, Ash, Dawn, and Brock for their help. Officer Jenny suddenly approaches the group. She scolds Marvel for working on a case without her permission. Marvel apologizes. Matthew tells Officer Jenny that Marvel was very helpful, and Officer Jenny is glad to hear that. She thinks that Marvel and Luxray are a real team now. Then Matthew invites everyone to a banquet. Ash can't wait to dig right into the food. Ash and co.'s journey towards Solaceon continues.
