The Underground Round episode.A failed experiment has left a town a virtual wasteland, overrun with Electrodes. Ash and friends lend a hand in ongoing efforts to extricate these explosive Pokémon, until Team Rocket arrives with designs to detonate all the Electrodes. Upon arriving at Hamlin Island, Ash and his friends learn of a ferry line that runs from Hamlin straight back to Pallet Town. On their way to the ferry, the trio comes to a road bridge, but it is blocked due to extremely dangerous conditions. With no other way to get to the ferry dock on the other side, Tracey suggests they cross it anyway. Just then, a huge Explosion blows apart the middle of the bridge. The three then find a rowboat and make their way across the small stretch of ocean. When they arrive at the town, they find it to be deserted. The three enter the ferry's waiting lounge but come across a locked door that prevents them from getting out to the dock and the ferry itself. As Ash and his friends ponder on how they will get back to Pallet Town, Togepi wanders out of the building and comes across a playful Voltorb, who rolls away. Seeing it as a game, Togepi runs after the Voltorb.

Upon noticing Togepi's disappearance, Ash and his friends search for it and soon find it standing atop the Voltorb. Ash checks his Pokédex for Voltorb's data, and the trio is shocked to learn that Voltorb may explode without warning. Misty attempts to pull Togepi off, but Togepi picks the Voltorb up with it. At that moment, the group is confronted by a horde of Electrode, who are all sparking with electricity. As Ash and his friends try to slowly retreat, a gust of wind knocks over a wooden sign, startling the Electrode and triggering a chain reaction of explosions. Just then, a man appears and throws out several Poké Balls, which release Diglett everywhere. Ash looks up Diglett on his Pokédex and finds out that they dig tunnels under the surface. The mystery Trainer then tells the Diglett to dig the Electrode underground. The Diglett create holes