Ash, Brock, and Dawn all seem to be having the same dream, in which the three Legendary Pokémon Azelf, Mesprit, and Uxie are calling them and asking them for help. When Pokémon Hunter J arrives at Lake Valor to catch Azelf on Team Galactic's behalf, Gary Oak is there to try and stop them. Unfortunately, Gary is unsuccessful, and Hunter J takes Azelf as a prisoner! Legend says that if one of the three Legendary Pokémon is taken hostage, the other two will appear. True enough-Mesprit and Uxie show up as soon as Azelf is captured. A powerful battle ensues, but Hunter J ultimately manages to capture all three Legendary Pokémon, and then gives the trio to Team Galactic. As Hunter J attempts to leave, Mesprit and Uxie unleash a powerful Future Sight attack, and Hunter J's ship goes down in flames.

Team Galactic now has everything it needs to call forth the Legendary Pokémon Dialga and Palkia. The process causes great pain to Azelf, Mesprit, and Uxie, as well as to Ash, Dawn, and Brock, who seem to be psychically connected to the three Legendary Pokémon. But Ash refuses to allow Team Galactic to continue, and our heroes begin a massive assault against them. The epic battle is just about to begin!