Larian Studios Forums Divine Divinity (English) Help/Tips/Tricks Stuck revealing Tingalf's supplier

How to reveal TIngalf's supplier?
I gave the letter to Macus,then talk to Tingalf,but he said there is another "deopt"where i have to find it...But i duunno where that place is?Can u guyz help me out?(i managed to open the "locked"chests after killing the 2 person who entered the cave)