Shadowbane (Paperback)

The city of Luskan has always been a den of pirates, thieves, and murderers. But lately, it has gotten even worse. A ship crashes ashore with nothing but corpses. Everyday people go crazy and kill those around them. The only signs found of even the most hardened criminals who walk the streets at night are bones.
Luskan's sister city, Waterdeep, sent a detachment to quarantine the unclean city--to let the filth die, rather than infect the rest of the Realms--but Myrin has slipped inside, declaring that she will save Luskan. Shadowbane follows, determined to save Myrin and therefore her pet city--even if he has to kill every rat in Luskan to do it.