For those not familiar with the game, here's a synopsis: you begin the adventure in the city of Phlan, on the shores of the Moonsea (a relatively small inland sea perhaps a quarter the size of the Mediterranean). The city is surrounded by monster-infested slums, ruled by an evil overlord named Tyranthraxus. Your characters get commissions from the Phlan city council to perform various deeds, usually related to clearing the slums of monsters and, ultimately (by this time your characters have advanced to 5th or 6th level) handing the big T a dirt nap.
Obviously, the campaign here with this carbon-based DM will be less linear, with more subplots, and the ability to leave the city entirely (which you could also do in the original Gold Box game, and level up rather nicely by stumbling across lairs in the wilderness and whupping monster ass).