A multi-part sidequest that extends across both East and West Tandor, beginning in Rochfale Town and ending in Silverport Town. The second part of the sidequest in Silverport Town provides some additional hints towards the larger backstory and what may have happened to the hero's mother, Lucille. Completing this sidequest is the only way to capture Garlikid.
Part 1: Rochfale Town & Route 6
When you first pay a visit to Professor Cypress at her laboratory in Rochfale Town, you'll meet a surprised Professor Bamb'o and Professor Cypress in shock over the theft of the laboratory's Pokémon. They're both upset and confused because Professor Cypress' most recent invention, the prototype Pokémon Speech Translator (PST) was left behind. She asks you to track down the thief, who evidence suggests took off west along Route 6.
As you head down Route 6, you'll encounter several agitated Owten that are guarding a small path northwards. At the end of the path lies a cave -- take the rocky steps up to the cave and challenge the Owten blocking the entrance.
Inside the cave, the thief reveals himself: a rare Pokémon known as Garlikid. He claims that he rescued the lab's Pokémon and challenges you to a battle.
You must defeat Garlikid to continue the Sidequest. If you lose against him, you will not get an opportunity to meet him again and capture him later in the game.
After defeating Garlikid and returning the stolen Pokémon to the lab, you continue on your journey to Bealbeach City.
Part 2: Silverport Town & Route 16
When finally arriving in Silverport Town in East Tandor, you discover a third Pokémon Professor in the Tandor Region: Professor Larkspur. Unlike Professor Bamb'o and Professor Cypress, Professor Larkspur is greedy and devious. His company is backed by a mysterious and dark benefactor. While he welcomes you to look around, claiming his laboratory must be far superior to the backwoods Laboratory in Moki Town, chatting with his aides suggests something sinister lurks behind the scenes. The lab workers are researching the capture of Pokémon that have already been captured, ways to control Pokémon, and a very distressed Owten sitting at the back of the lab.
Upon speaking to the Owten, Professor Larkspur jumps in surprise, realizing that you are using Professor Cypress' experimental PST. At first he offers to pay you for the PST or a choice of any of the rare Pokémon at the lab but realizes that you are unlikely to part with an important research tool you have been entrusted with. He then asks you to leave.
As you head north towards Lanthanite Cave, you'll see several thugs standing along the sides of the path. As you approach, they surround you, grab your belongings, and knock you out. You wake up a short while later in a cell in the bottom of Professor Larkspur's laboratory, where the professor tells you he didn't want to hold you prisoner, but that he has incurred considerable debt with his mysterious backers, and needs a breakthrough before they come to collect. He notes that he just plans to hold you temporarily to prevent you from interfering until he can reverse engineer the PST. He also tells you about his more shady research: trying to find a way to sap the will of Pokémon and force them to fight against their wishes.
After the professor leaves, you're left to wander around your cell. There's not much to do, so just take a nap in bed. A guard will wake you with some food -- underneath is a Secret Note telling you how to escape your cell.
To escape from Professor Larkspur's dungeon, break down the cracked wall behind your bed to reveal an opening to another hallway with several cells. One of the cells is holding Garlikid, who immediately recognizes you.
Access the computer console and enter the code from the Secret Note (092) and initiate the "Release Door Control." While you can't understand Garlikid without the PST, he'll still join you. Be sure to take a moment to read the other options in the computer console, which tell of a mysterious Specimen 092, a brilliant female scientist, an intrepid investigator, an accident Professor Larkspur initiated from afar to cover up his unethical research, and a mysterious backer that Professor Larkspur kept hidden from everyone, including the scientists working most closely to him.
Take Garlikid back through the crack in the wall to your cell and he'll bend the bars so the two of you can escape. Make your way through the lab, rescue your Pokémon, defeat Professor Larkspur's scientists, and battle Professor Larkspur himself.
After defeating Professor Larkspur, he and his team will flee, and Garlikid, deciding that the two of you will travel throughout the Tandor Region together rescuing Pokémon, joins you permanently.
Note: Before you recover your Pokémon to battle Professor Larkspur, Garlikid will battle on your behalf. Garlikid is a level 50 Grass-/Fighting-type Pokémon, making him perfect for battling against Professor Larkspur's scientists, who all use Normal, Ground, Rock, and Steel-types. The Garlikid you use in the battles here is not the same Garlikid that will join you on your travels later. The Garlikid you receive later will have a different Nature and IVs, and will not be holding an item if you gave one to the Garlikid while breaking out of the lab. Any item held by Garlikid will disappear when you get your main party back.
After defeating Professor Larkspur he suggests he might join the Kanto Region's Team Rocket from Pokémon Red, Blue, and Yellow.
Professor Larkspur's research into capturing Pokémon that belong to other Trainers and suppressing the wills of Pokémon may indicate connections to Cipher, the antagonists of the Pokémon Colosseum games.