From the introduction:
The Velverdyva spills into the Nyr Dyv and the adventurers are closer to Greyhawk than ever before. Farms begin to dot the southern shore, while fishing villages dominate the northern. As night sets in, the player characters see that one of the fishing villages is aflame and raiders are gathering both valuables and people. The tragic event ties closely to the party’s next destination, the Free and Independent City of Dyvers, where some vile evil is at work in the shadows of this great city. Will the player characters recognize the evil that plagues Dyvers? Will they track down the perpetrators of these foul deeds and put an end to their wicked ways? Find out in these very pages: Chapter 13 of the Great Flanaess River Adventure!