Pokémon Mystery Dungeon: Blue Rescue Team and Red Rescue Team/Mt. Steel

Between Missions
Once back from the last mission you sleep and have a strange dream. It feels familiar but nothing can be made out. Upon waking up the dream is forgotten.

Your partner has been waiting to meet you outside. Both of you find some disappointing news at the mailbox. There are no new missions or mail of any kind today. The partner expected this since your rescue team was only recently made. Instead he is going to give you a grand tour of the Pokémon Square and most importantly, the bulletin board beside the Pelliper Post Office.

Going on random missions from the bulletin board and wandering around town is now available. To begin the Mt. Steel story arc just go to the far right to the Pelliper Post office's bulletin board. Do a mission in Tiny Woods or Thunderwave Cave. If there are multiple missions for the same location on the bulletin board you can accept all of them and do them all in one outing. After the mission and you get home the Mt. Steel story arc will begin.

Mt. Steel
After given the option to save you have the same dream. An earthquake startles you out of your dream. In the morning you awaken to a voice that seems to be coming from nowhere. It turns out to be an upset Dugtrio that is distressed by the disappearance of their child, Diglett. Once outside your partner joins you and the Dugtrio finally.

A Skarmory took Diglett and flew to the top of Mt. Steel. Since the slopes are made of rock Dugtrio can't go up there. Your rescue team has a new important mission.

Boss Battle: Skarmory
This is the very first boss you have fought yet, and will undoubtedly be the toughest foe you have faced yet. Since his type is Steel/Flying, Cyndaquil, Charmander, and Torchic will have it much easier than the rest. If you picked a Grass type, you had better have a strong Fire type team mate to deal out the damage.

After Skarmory falls, he will fly off, giving you access to the Diglett. After saving it, you will warp back out of the dungeon, and meet the greatly relieved friends.