With the Sinnoh League behind them, Ash and friends take a ship back to Dawn's hometown of Twinleaf. A crisis emerges, however, when a group of Tentacruel attack the ship and poison many of the Pokémon on board. With no other doctor on the ship, Brock is the only one who can help those Pokémon. Will he succeed before it's too late?

Back in Twinleaf Town, Ash, Dawn, and Brock finally come to realize that their journey together is over. Everyone is sad about this, especially Piplup who is overwhelmed with tears. However, as one journey ends, one is also set to begin.