Pokémon Season 1 Episode 13

Mystery at the Lighthouse
When a Krabby that Ash catches disappears, he goes to a nearby lighthouse to see if it reached Professor Oak’s lab. The keeper of the lighthouse is Bill, a Pokémon Watcher who is searching for a mysterious Pokémon that sometimes appears by his lighthouse. Just as this mysterious Pokémon answers Bill’s call and approaches the lighthouse, Team Rocket appears and tries to capture it. Injured, the Pokémon loses its trust of Bill and vanishes forever, though Bill intends to keep an eye out in case it ever appears again.