WATCH_DOGS

I won't go into ridiculous detail here - if you'd prefer video guides I've added the best ones I found at the end (not mine, credit goes to the uploader on YouTube)

There are two side investigations in Bad Blood: Fox Hunt (investigating Fixers after Aiden Pearce) and Council of Daves (about the DedSec group).

These work in a similar way to the investigations in the main game - that is, there will be icons on the map marking locations to find either a QR code or a hackable item. You'll get both types in each investigation so pay attention to the details given on-screen when you get to the marker as to what you need to find

These are mostly really straightforward (there's one QR code near the dam in Pawnee that was a little bit of a headache - hint, look for a camera in the trees near the boathouse, it's the first one in the video linked below) and once you've completed 5 in each investigation a final mission will appear.

For me the achievement did not unlock on completing the second investigation however it did pop when I next turned the Xbox One on, so don't panic if you've completed everything and it doesn't seem to have appeared.

Downvoting? Leave me a comment on where I could improve!

This Achievement is for completing 2 investigations:
1. Fox Hunt - Available after Act 2 Mission 1
2. Council of Daves - Available after Act 2 Mission 2
Each investigation has 5 collectibles associated with them and a final mission which unlocks after finding all 5, this achievement should unlock after completing both of those.
The in game progression wheel tracks the collectibles but does not show the missions meaning you will have 5/5 on both investigations before actually completing the investigations.