Ash and the gang are still on their way to Mossdeep when Max says that, according to the PokeNav, there are three islands approaching called the A, B, & C Islands , one of which has a Pokemon Center. However the journey is interrupted when a bunch of kids ride past on a bunch of Huntail and Gorebyss, which both evolve from Clamperl. While at the Pokemon Center, the group hear a brother and sister arguing about if Huntail or Gorebyss are better than each other, which is a rivalry between the other two islands. While attempting to mediate the quarrel, Ash and the others meet up with their old friend Professor Birch, who explains he is on the island to investigate the mystery of Clamperl's evolution... (thetvdb.com)