A very nice take on how to introduce investigations and mysteries to FIST. The list of training available allows your character to have another layer of uniqueness and usefulness in particular situations. 

Having a list of possible explanations for how a character can succeed in investigations not covered by its training is a useful add-in, as well as advice on how to treat an investigation as a GM.

It seems to be as much an interesting expansion to FIST as a good manual on how to make good investigation scenarios.

ENIGMA is an effort to merge FIST with GUMSHOE for more mystery focused games. It seemed a bit unwieldy as I see them as very different systems, but your mileage may vary. 

There are still plenty of ideas worth considering even if you don’t use the investigative specialties. The “Insufficiently Trained” section has ways of delivering clues to your agents and that’s where things get gonzo. Sassy robot partners, demonic familiars and psychic powers are just some of the ideas that would fit in with any mission or team.

Enigma Team is an alternative game mode for FIST that focuses on intelligence gathering and espionage over action-first tactical engagements.

The PDF is 16 pages, with a straightforward layout and dense but well organized text that's easy to read.

Contents-wise, Enigma Team adds a new wrinkle to the lore, where FIST isn't just an organization composed of freewheeling do-gooder mercenary strike teams. It also works in conjunction with Enigma Teams, who gather information for those mercenaries to use.

The main mechanical feature of Enigma Team is investigative trainings, which give a bonus to certain avenues of investigation. There's a long list to pull from, with some headings spelled out in more detail than others.

There's also a detailed list of other sources teams can call on for help, ranging from computers to aliens to summoned spirits.

For GMs, there's a lot of discussion on how to structure an investigation, and how to make its moving parts satisfying for the players to interact with.  None of this is really mechanical, but it's good advice, and worth the read.

Overall, if you want to play a more gumeshoe-y version of FIST, or if you want some material for an unusual variant mission to break your normal campaign's structure, I'd recommend giving Enigma Team a shot.

You got GUMSHOE in my FIST!

Not a bad thing, it turns out. I think most people would have more fun bolting this on to Vanilla FIST, and it's hard to see how it would wind up as a detriment.  Could use an example scenario or two to show how the framework works in practice. 

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.