The Endless Well (d20) (2007)

From the introduction:

A Short Adventure for Four 5th-6th Level Player Characters...Though small and relatively close to the small town Arden, the Endless Well caverns have rarely been explored, that is until recently. A few months ago several farmers, who have land that boarders on the Arden River, have been complaining that many of their livestock have been going missing. As no remains of the animals could be found, wolf and undead attacks were ruled out as a likely cause.

User summary:

The fourteen-page PDF file is distributed in a ZIP archive that also contains one overland and five dungeon maps in JPG format.