From publisher blurb:
The Crossing is a Pathfinder Roleplaying Game compatible adventure for 4-6 characters of 3rd to 4th level, who will advance an average of one to two levels by completing this module.
Merchant vessels have been disappearing on the river west of Ferryport. There are rumors of a river pirate, but when the adventurers investigate they will find far more behind the disappearances than the guild masters of Ferryport could ever imagine. Deep within the Miragol Swamps, in a place of great power, lies a long forgotten tower with ancient secrets that have begun to be unearthed by a treacherous former lord of Ferryport. Under his command are foul creatures only remembered in ancient legends and folktales. Will the heroes be able to uncover his plot in time to save the region from war?
This adventure is Part Three in the Ferryport Adventures, Return of the Fey adventure path, which is set in the Dark Return, introduced in The Elves of Uteria sourcebook; but it can easily be played as a standalone adventure in any fantasy world setting.