Ash and Goh arrive at Canalave City, where they meet Dawn and Cynthia as they participate in the Sinnoh Festival. Meanwhile, Team Galactic corners Heatran at Stark Mountain as Saturn catches it to enact their latest plan.

Ash, Goh and Dawn, after getting a mysterious call for help from the Lake Guardians, meet with Brock. Team Galactic begins their plan to open a portal to bring back their leader Cyrus, but the intense power from the experiment causes Saturn's Heatran to go on a rampage as it escapes.

Ash, Dawn, and Goh, with help from Cynthia and Brock, try to stop Team Galactic, as well as save Heatran from its frenzied state, to no avail, then Arceus appears to the group's aid.

Arceus uses its powers to impede Heatran as Ash, Goh, Dawn, Brock, and Cynthia work together to save the Legendary Pokemon and defeat Team Galactic's Commanders, leading to the team's rearrest and the five saving the Sinnoh region.