She and her older sister Lena were resting at the same Pokémon Center as Ash and his friends were, when her bag containing a Pichu she cares for got accidentally switched with Bonnie's bag containing Dedenne. As she and Lena left and were walking down the street, Lyn noticed Dedenne was in her bag instead of Pichu. Confused, she quickly ran off to find Pichu while Lena was talking to a friend.
While she was still worried about Pichu, Lyn decided to care for Dedenne by giving it food and tying a ribbon in its ear. Lyn then decided to go back to the Pokémon Center to find out more information about where Pichu went. She couldn't find the Pokémon Center back however, and she then found out Dedenne had ran off. She found it sleeping in a store with stuffed Pokémon dolls. Continuing their search for Pichu and Bonnie, Dedenne suddenly noticed an array of electric waves in the air, created by one of Clemont's inventions in an attempt to lure Dedenne to them. Attracted by it, Dedenne ran off once again, in the direction of the source of the waves.
On the way, Dedenne passed through a grape orchard to eat some grapes, but it was attack by a wild Beedrill. Initially disposing of it with Thunder Shock, the Beedrill angrily returned with a whole horde of Beedrill. As Lyn and Dedenne ran away, Lyn tripped and was about to attacked by the Beedrill when she and Dedenne were saved by Ash's Pikachu. Ash, his friends, and Lena and Pichu had finally found Lyn. Lyn was happily reunited with Pichu, while Bonnie was reunited with Dedenne. Afterwards both girls burst out in tears because of the whole incident. Then the group and Lyn and Lena decided to have dinner together.