The Shaft is a FIST module about descending into a lightless underground facility.
The PDF is 2 pages, with an extremely polished layout and a useful, technical-looking map.
Contents-wise, this is a mission that leans on the GM's description and pacing. The environment is scary, but only if you take your time with it. The module's monsters (cosmic debris from elsewhere) aren't a huge threat, but they do establish tone and make it clear that the facility *is* dangerous.
Overall, if you want a more somber, survival-horror-y FIST experience, or if you want to run FIST for a new group, I'd strongly recommend giving this a look. With some conversion, I think it could also work as a fairly deadly Delta Green scenario.