Located in the Warehouse just south of Gantolandan's House in Baldur's Gate South East (x 790 y 1950), he gives you the Nadarin and the Basilisk subquest. To complete the subquest go to the Docks in Baldur's gate and enter the north most warehouse. Make sure to have a Scroll of Protection from Petrification or a Potion of Mirrored Eyes to stop your characters from turning to stone. You will gain 1300 xp and depending on your NPC reaction your will get either 1800gp or 500 gp and Boots of Stealth as a reward. An NPC reaction of 15 or above gets you the 1800gp while an NPC reaction below that gets you the 500gp and Boots of Stealth.
In Enhanced Edition, you always get 500GP, no matter your Reaction. You can also simply pickpocket the Boots of Stealth off of him.