From the Publisher:
Ancient gods, giants, fey spirits, and a mysterious fog-veiled isle where a long forgotten dark magic lurks... Based loosely on ancient Celtic mythology, Tribes of Danu is a series of OGL 3.5 Adventure Modules. The modules and expansions are designed so each may function as stand-alone adventures, but are intended to be played as a serial. In A Lesson Learned, the PC's rescue a lady in distress (a forest fey), and find out her reward is a double-edge sword. If they can out-smart the cunning vixen, there's plenty of treasure to be had, however if they aren't clever then they might just end up permanent residents of the Isle. This module is intended as an expansion to “Heart of the Neolith”. However, it is also a stand-alone adventure appropriate for up to four characters of 2nd level or higher.