Investigating the Merchants' League Estate

This quest is gained by talking to Aldeth Sashenstar in front of the Merchants' League Estate. In order for him to be there, Gorion's Ward and their party must have sided with him at his hut in the first area of the Cloakwood; otherwise, his brother, Dabron Sashenstar, will be in Central Baldur's Gate and will attack your party. When you talk to Aldeth, he'll say that something is off at the Merchants' League and that his two partners, Irlentree and Zorl, have been acting weird and making bad business decisions. You'll be asked to investigate this and invited inside the building. Once inside, go to the second floor; in a locked desk in the southern room, there are documents from which you will learn the truth: Irlentree and Zorl are actually doppelgangers. From here you can choose one of two paths:
* Talk to and give the documents to Brandilar - a guard on the second floor. He wants you to kill the doppelgangers right away and, immediately after the conversation, the merchants will revert to their true forms and become hostile;
* Give the documents to Aldeth, and he will lead you the third floor to his fake anniversary party, where you will confirm what was in the letters and learn that the doppelgangers were sent by their master, Rieltar. After the dialogue, all the merchants in the room will revert to their true forms and turn hostile.
There are two major tactical advantages tied to the Brandilar option:
* You will be alone with the doppelgangers, which means you can use fireballs and other area of effect spells. When using the Aldeth option Aldeth and Brandilar will come with you and one of them or both are likely to get caught in the crossfire, which turns them hostile.
* Addtionally, the Aldeth option lands you in the middle of all doppelgangers and very quickly your weaker characters will be swarmed and interrupted;
No matter the path you chose, after you have killed all the doppelgangers, talk to Aldeth to get your reward.
As of V2.660 of the enhanced edition, he can be pickpocketed for a diamond and a Potion of Heroism when he is outside the estate, on the second floor, and the third floor, for a total of three times.
== Bugs ==
Killing the doppelgangers before they've had a chance to transform (e.g. killing Zorl before you've reported to either Aldeth or Brandilar) may bug this quest, as the kill will not be counted. Similarly, charming Irlentree will yield the same result, as he will not transform, turning hostile instead after the effect wears off. 
Can be fixed with setting GLOBAL Variable ALDETHDOPPLE - for the Enhanced Edition use the console command C:SetGlobal("ALDETHDOPPLE","GLOBAL",20)