First, finish the slave trader quest, that should unlock a new quest that continues from the slave quest. When you infiltrated the gold mine, keep looking for a person named alynn before finishing the quest. After that then alynn would be available in the desert city
Michael is the slaver boss, if you become a belly dancer and sold yourself to a man with head wrap, you will notice he has a red flame tattoo on his face. Then you can go to the tattoo parlor and ask for the same tattoo, must be reversed and must be dark red. Then buy a desert headwrap and went to the desert. If you meet a slaver with a wagon, show him your face tattoo and he will either bring you to the slaver base or slaver hideout with a map to the base. Though the wagon slavers won't approach you anymore if you beat them up before. Michael is in the base. You can also find the hideout with enough sense.