From the publisher's website:
A new mini-module by Abashima Press publisher Eric Haddock takes PCs to the Hidden Coast, where they discover the truth behind a mysterious excavation and what it has revealed. Drop this free online adventure, The Secret in the Windswept Wall, into any setting you like.
Sionaas, a powerful wizard, started construction of a tower and dungeon in the nearby mountain range, the Windswept Wall. He recruited a large number of villagers for labor from Poisson, the nearest point of civilization in the area. He pays well and treats them kindly. Two days ago, something terrible happened at the site and a messenger was sent to Poisson:
Workers trapped in cave-in -- send help.
A surprise is waiting for the PCs once they arrive on site...