I have a question, when you enter the Bridge District there is a liutenent that warn you that tere are murderes around kiling the beggars.

I have solved that discovering that the murderer was a guy that was in some store, i have killed him and so on, but my true dilema is when you kill him in the ground is a letter with a scheme, something about a name of a guy, i have solved that to but after you guess is name and say it to him he says something about the blood of a silver dragon and the skin of an unfinished armor to complete something, where can i find both?

<font color="gold">SPOILERS
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You should find the skin right under the bed next to where you found the note. The Silver Dragon blood is to be found later in the game, in the Underdark. To get it, you must kill a good Dragon, so you should be evil to wear it.
IMO, it's not even a good armour. ;) </font>

the human flesh (unfinished armor) is in a bed in the tanner's shop and the blood is on the silver dragon herself of course (you'll eventually meet her in the course of the main plot) to make and wear this armor however you have to be TRULY evil

tip: use Tab to highlight all doors/cupboards/chests/chestlike items
on the screen, thus not missing important treasure like the human flesh

Actually the human skin is in the bed, but it doesn't get hilighted by hitting tab because it's a "interact" thing not an "openable / rumage through" thing.