Find the Kidnappers Who Buried Tirdir - Baldur's Gate 2 Side Quest
Find the Kidnappers who buried Tirdir is a Side Quest that begins in the northern portion of the Graveyard District in Athkatla. When you pass by a recently dug grave you'll get a dialogue pop up starting with, "Nearby you see an open grave. A chill runs up your spine as you hear a sound emit from it." Mouse around the area where you see the open grave (and this dialogue pop up) and you'll see that you can interact with it.
If you're new to the game when the cursor changes to 2 arrows in a circle pointing to one another it means that you can interact with this area in the environment. That's what you'll see when mousing over this area. Upon clicking on it Tirdir will climb out of the grave and speak with you.
Ask Tirdir, "What can you tell me about them?" and it will get you a Piece of Red Cloth that is needed for the next 2 parts of this quest. Before we're able to go to the Bridge District and confront the kidnapper you'll first have to speak with Sethle whose in the northern portion of the Graveyard District. Go a tad bit northeast of Tirdir and you'll find Sethle standing outside a tomb.
Sethle will tell you that the man you're looking for is found in the Bridge District.
The kidnapper himself is a man by the name of Am-Si whose wearing a full red outfit. You can find him in the southern portion of the map standing on a walkway near the water, a picture of him is shown above. When you talk to him and ask him about Tirdir he'll flee inside of a nearby building to the south and you will have to pursue him.
Inside the building you'll find the other people that Tirdir was working with, they'll kill Tirdir when you enter (assuming you didn't kill him outside) and then leave the building. When you go outside you'll be able to force attack both these NPCs and it's strongly recommended you do as Reti will drop Senses of the Cat boots.
On the 2nd floor of this building you'll find another NPC by the name of Lady Elgea, she's the most recent victim of these kidnappers and you'll be given a few different options to proceed with her...
1. Free Lady Elgea for 16,750 EXP
2. Tell her you haven't decided then immediately free her for 8,500 EXP
3. Collect the ransom yourself (this route can get you Silver Pantaloons)
The Silver Pantaloons that you get from this quest are involved in an easter egg that spans both BG1 and BG2. Suffice to say that this item is completely useless for you unless you imported a save file from BG1 that had the Golden Pantaloons on it. If you decide to go this route and ransom Lady Elgea for the Silver Pantaloons then you'll want to grab the Ransom Note from the cabinet near Lady Elgea and take it to the Slums District at night.
Here you will meet Welther outside the Copper Coronet (pictured below).
Giving the ransom note to Welther will result in you losing 2 points of Reputation and you getting the Silver Pantaloons. At this point in time you're able to return to the Bridge District and enter the building with Lady Elgea again to fight a group of Amnian Soldiers and Cowled Wizards. You will not suffer any additional loses of Reputation for fighting these enemies.