The Pen is a FIST mission themed around animal research.
The PDF is 2 pages, with a well organized, easy to read layout and some helpful graphics and nice interior art.
The mission is GM-friendly in its design, and it includes multiple hooks, complications, and a hook generator.
For the most part, the meat of The Pen consists of a few scraps against mutated animals in a military industrial environment, but the concept for The Pen is nicely creepy and there are a lot of opportunities to weave elements from The Pen into other missions, stretching its shadow across a longer campaign narrative.
Overall, if you're looking to include mutated animals in your campaign, or if you want a new-player-friendly mission environment to drop a oneshot team into, The Pen is a great pick. It's absolutely worth adding to your FIST missions dossier.
Minor Issues:
-Page 2, Docile Automaton, "inmates violent tendencies" inmates'