The Mystery of the Missing Cubchoo! (Japanese: ソムリエ探偵デント！消えたクマシュンの謎！！Sommelier Detective Dent! The Mystery of the Missing Kumasyun!!) is the 88th episode of the Best Wishes series, and the 745th episode of the Pokémon anime. It first aired in Japan on July 19, 2012 and in the United States on November 17, 2012.
Our heroes are staying at Cynthia’s house while they prepare for the Pokémon World Tournament Junior Cup. After Ash and Dawn have a practice battle that ends in a draw, a worried young neighbor named Chris comes by, looking for his lost Cubchoo. The boy tells them Cubchoo somehow got out of its Pokémon house overnight, although there’s only one door and Chris is sure he locked it from the outside.
So...who will come to the rescue? Why, Connoisseur Detective Cilan, of course! After much questioning of the details surrounding the “case,” Cilan finds a small tunnel under the wall surrounding the Pokémon house, leading out to the forest. Our heroes investigate and find a surprisingly tame Beartic eating Berries nearby. Cilan decides it must have taken Cubchoo, but Dawn points out that Beartic is far too big to fit through the tunnel. Then he announces that Beartic is the missing Cubchoo, and that it must have evolved after it escaped! But when Beartic won’t return to Chris’s Poké Ball, it becomes clear that Cilan is wrong again.
Finally, they spot Cubchoo when it comes running by, playing with a wild Larvitar! The two Pokémon are obviously good friends, and Cilan deduces that Larvitar must have figured out how to open the door to Cubchoo’s Pokémon house so they could play together. He declares the mystery solved, and Ash wants to celebrate with a battle! Chris and Cubchoo have never battled before, so Ash and Scraggy battle against Larvitar to show them how it’s done. The battle ends in a draw, but Chris and Cubchoo are excited about learning to battle too! Ash and Iris suggest that the two of them set off on a journey together, and Chris says they will—as long as Larvitar comes with them.
Meanwhile, Team Rocket appears to be getting closer and closer to its mysterious target...
During their stay in Undella Town, Ash and his friends spot a young boy named Chris frantically searching for his Pokémon Cubchoo. Concerned, the gang offer to help. Cilan takes out his detective equipment and begins an investigation of Cubchoo's Pokémon House. He ponders if it's possible that Cubchoo was kidnapped. Chris tells him it's impossible since there are security cameras and burglar alarms along the walls of the outside perimeter.
The gang spot a hole dug under the wall that's big enough for a small Pokémon to go through. Both Pikachu and Dawn's Piplup are able to crawl under the wall and onto the other side into the forest. Cilan comes up with several scenarios as the Pokémon notice a trail of food remains leading into the forest. They alert their Trainers and the humans follow the trail. At the end of the trail is a sleeping Beartic with food remains scattered around it.
After Ash scans it with his Pokédex, Cilan concurs that Cubchoo must have evolved and tells Chris to call back his Pokémon. Chris attempts to do so but it doesn't work indicating that the Beartic isn't his. Soon, Chris's Cubchoo and a wild Larvitar are seen running out of a nearby bush and chasing each other playfully. Chris is reunited with Cubchoo and Cilan explains that Larvitar must have let Cubchoo out of the Pokémon House. Iris and Ash ask if Chris ever had a Pokémon Battle before and he replies that he hasn't.
Iris explains that battles are how Pokémon grow. Ash challenges Larvitar to a battle with Scraggy and Larvitar accepts. Scraggy runs towards Cubchoo with a menacing look as Ash points out Larvitar is his opponent. Chris and Cubchoo watch as Ash starts the battle. Scraggy uses Headbutt and Larvitar attacks back with Bite. Cubchoo cheers for Larvitar as Iris praises good friendship. Ash orders Scraggy to push Larvitar off and use High Jump Kick. Scraggy misses as Larvitar retaliates with Sandstorm.
Ash orders a Focus Blast and Larvitar counters with Hidden Power. They both get hit and are too tired to fight anymore which results in a draw. After the battle, Cubchoo punches the air with a competitive look on its face indicating it is rearing to go too. Chris smiles and tells it maybe later and that they should go home first. Larvitar and Cubchoo throw fake punches at each other in playful way as Ash and Chris talk about Chris starting a journey. After encouragement from everyone, Chris states that one day he will go on a journey of his own with Cubchoo and Larvitar.
In the dub, when Dawn tells Iris how Cilan reminds her of Brock, she refers to him as "a guy named Brock" as if she was mentioning him for the first time to Iris. However, she actually first mentioned him to her and Cilan in the previous episode.