An explosion occurs as a rare Pokémon Riolu is stolen from a laboratory. The group of men that stole Riolu is discussing about how Riolu is a fool for trusting them. Riolu overhears the group talking about how they tricked it. It gets mad and busts its way out of the truck and escapes.

Ash and co. are continuing their way through the Sinnoh region. They suddenly come across the Riolu, who is injured. Ash tries to help it, but Riolu fights back with Aura Sphere, an attack that is usually learned by Lucario. A boy in a green coat suddenly appears, and Riolu runs away. Ash wants to go after it, but the boy tells him that he will handle it. The group hides behind a bush, as they watch Riolu sitting on a tree branch. The boy says that Riolu just wants to go back to its home.

Suddenly, Pokémon Hunter J's henchmen appears. They have come to capture Riolu. A Crobat is sent out, and it attacks Riolu. Pikachu attacks Crobat back with Thunderbolt. The henchmen are getting frustrated, so they send out more Crobat. The boy reveals himself as a Pokémon Ranger. Using his styler, he captures an Ariados and Nincada to defeat the henchmen. Then the boy presents Riolu with a wooden figure of itself, a token that must be important to Riolu. It is a way to get Riolu to trust him.

The boy introduces himself as Kellen, and he takes Riolu to a safe place. Kellen knows that it will take some time for Riolu to trust people again, since it's been through some tough times. Riolu stares at the doll that Kellen gave to it. Ash realizes that the doll is very important to Riolu, since it was able to see its memories through its aura. Pokémon Ranger Solana calls Kellen about the latest update on the search. She reports that they found the location of Hunter J's client, and she and Officer Jenny are headed there now.

Hunter J's ship finally arrives, and Ash and co. know that she plans on taking Riolu. So Ash and co. decides to take a boat out into the lake. Kellen explains the whole story about Riolu to Ash and co. and how it ended up being the target of so many criminals. His mission is to transport Riolu back to its home safely, and so they are headed towards headquarters where that will happen.

Suddenly, four Sharpedo burst out from underneath the water and destroys the boat. The Sharpedo belong to Hunter J. Kellen captures a Floatzel, and the group begins to swim away. The Sharpedo attacks Ash and co. with Aqua Jet, but Pikachu manages to shock them down. Suddenly, Hunter J herself appears on her Salamence. She fires her gun at Riolu but misses. However, the explosion causes Riolu to lose its doll. Riolu chases after it, and Ash follows it.

The current is too much for Riolu, and it sinks underwater. Ash and Buizel dive underwater, and they rescue Riolu. When Riolu wakens from its sleep, Ash gives the doll back to Riolu. Meanwhile, Hunter J and her henchmen are discussing where Riolu might be hiding. They find Ash and Riolu running through the forest, and Hunter J comes up with a plan. She uses her Salamence to create a huge wildfire in the forest. The Fire Blast from Salamence blocks Ash's escape. Ash refuses to give Riolu to Hunter J, so she commands Salamence to use Flamethrower. Will Ash be able to escape Hunter J and return back Riolu safely back to its home?