Ash and friends have finally arrived in Castelia City. While exploring the city they run into Burgh. After hearing a noise underground, they go into the sewers to see what it was and find a wild Venipede. It is injured, and even though they heal it, the other Venipede in the sewers become upset and begin attacking the city above. Ash, Burgh, and his friends want to stop the Venipede and get them out of the city without hurting them, but Castelia City's mayor has his own plan in mind.