A solid investigative module for FIST. ENIGMA not only changes how you act in investigation scenes in a game but also adds context. Instead of rolling to resolve a mystery, ENIGMA equips characters with different 'training' choices and then gives them clues related to it. This makes investigations more rich and engaging without glancing over the process.
It's very well laid out with backstories for ENIGMA the organization, how it relates to your characters, training types, strange familiars and concise tips on how to run an investigative scene for the GM. I'm surprised this isn't a system in itself since it could very well function outside of FIST and without it.