While at the schoo, Ash learns of a powerful trainer who has come to Melemele Island. Ash eagerly finds this trainer and challenges him to a battle. The battle is strong with the trainer's Z Move coming into full force but soon after the battle starts, Lillie appears and confirms that this trainer is her brother, Gladion. Why is Gladion here?

Ash and his classmates go on a camping trip in the forest. The trip does not start out well when Lana scares them all with a ghost story about a traveler who had all his energy drained from him while he was asleep. However, they have no idea that they are being spied on by a mysterious Pokémon. One by one, the gang except for Lillie is attacked, knocked out, and their energy drained from them. The culprit turns out to be a hungry Morelull. Ash figures out a way that the Morelull can get all the energy it needs from him, and later the gang finds out why the Morelull need so much energy.