After the DDs are dropped off by the Trailmon they find out that they are in a cave of some sort with no way out. They look around for a while trying to find a way out when from out of nowhere a blast of water hits JP and Tommy, it was a blast created from Whamon who was in a pool of water in the middle of the cave. After Agunimon and Lobomon calm Whamon down, Whamon tells them how he got stuck down there. After the story something happens to Whamon and the pool of water disappears leaving Whamon with no water. It was Grumblemon. He came to get his beast spirit back. Agunimon and Lobomon go to stop him but are stopped by Arbormon. Grumblemon then turns a bunch of rocks into Rockmon (aka Golemon). JP and Tommy have to fight them since Agunimon and Lobomon are fighting with Arbormon who just changed into Petaldramon.

They fight off the all of the Rockmon except for the one that Grumblemon's on Beetlemon then evolves back into JP who is still hurt because of the blast of water from Whamon earlier. Grumblemon then goes to hit JP when Whamon hits Grumblemon with a water blast flinging him into the wall. That's when JP sees the Beast Spirit of Thunder. Whamon had accidentally eaten it when he was eating seaweed before he got stuck down there. Grumblemon also sees it and goes after it. JP holds up his D-Tector and gets the Beast spirit of Thunder He then evolves into MetalKabuterimon and defeats Grumblemon, then slides back into Beetlemon and scans Grumblemon's fractal code turning him into a Digiegg. Zoe then gets her spirit back. The cave then starts to crumble because of the battle. A bunch of rocks fall on Petaldramon and water starts to poor in. The DDs all awake inside of Whamon's mouth. He tells them that they are getting closer to an island.