When Lawrence III's scheme to capture the Legendary Pokémon Lugia upsets the balance of nature, it is up to Ash Ketchum and his friends to save the world.

In order to escape a greedy Pokémon hunter, Celebi must use the last of its energy to travel through time to the present day. Celebi brings along Sammy, a boy who had been trying to protect it. Along with Ash, Pikachu, and the rest of the gang, Sammy and Celebi must encounter an enemy far more advanced than the hunter, with the fate of the forest hanging in the balance.

Ash, Pikachu and the gang try and stop a pair of thieves hiding out in the canals and alleyways of Altomare, the age-old water capital. Joining the adventure are two new legendary Pokémon, a pair of siblings named Latias and Latios, who serve as peacekeepers and protectors of the Soul Dew — a priceless treasure with a mysterious power.

Determined to prove its superiority, a bio-engineered Pokémon called Mewtwo lures Ash, Pikachu and others into a Pokemon match like none before.

When the sadness of her father's disappearance gets to Molly Hale, she unknowingly uses the Unown to create her own dream world along with Entei, who she believes to be her father. When Entei kidnaps Ash's mother, Ash — alongside Misty and Brock — invade the mansion looking for his mom and trying to stop the mysteries of Molly's Dream World and Entei!