Irenicus' Dungeon, Level 1 | Irenicus' Dungeon, Level 2 | The Elemental Plane of Air
OVERVIEW OF CHAPTER 1
In the first chapter in Baldur's Gate 2 - Shadows of Amn you find yourself trapped in a dungeon and must fight your way out. There is no time limit and you can rest without risk almost anywhere in the dungeon, so long as there are no hostile creatures around.
The chapter begins with Imoen freeing you from your cell and, at least for the purpose of this walkthrough, it ends when you escape the initial dungeon. Officially, Chapter 2 doesn't begin until you enter the Slums District but it makes sense to treat Waukeen's Promenade, the area you emerge into, as part of Chapter 2.
You can view Chapter 1 as a crash course on how to play Baldur's Gate 2 - Shadows of Amn. You get to assemble a party, equip weapons and armor, make choices based on your protagonist's morality, and fight a variety of not too difficult enemies.
For an overview of how to escape Irenicus' Dungeon as quickly as possible, please see this page. If you wish to explore the dungeon thoroughly and do the other quests available in this part of the game, please see the Quest List and the area maps starting with Level 1 of Irenicus' Dungeon.