--- First achievement of the Leviathan DLC, MISSABLE ---
In the first room you can control Shepard, you need to search for clues for the system you need to go to, and enable/disable found clues on a galaxy map interface. Simple point-and-click around the house. After you have narrowed it down to five or three, you can leave the place. Do NOT leave yet! (If you did leave but didn't complete the first combat mission, you can return and still get this) You need to narrow it down to one. There are 6 filters total, and of those you need the following:
Reaper Activities ON
Prothean Activity OFF
Element Zero ON
Rachni Activity OFF
Blackout Crimes OFF
Creature Sightings ON
(you don't actually need to find those that are set to off, but it can't really be avoided if you touch everything with orange brackets on it)
All of these are really simple to find by point-and-click, reaper activities is the only slightly more cryptic one. For this you need an encryption key for a datapad, which is found upstairs in a drawing by the scientist's daughter. When you have it, go click on the datapad again.
The complete map will end up looking like this:
...which tells us Dr. Bryson keeps his galaxy map upside down, since it's really nowhere near there in Normandy's galaxy map.
There is another similar scene in the DLC later on, and it might also be a possible trigger for this achievement, if you missed it in the beginning. Needs further info to confirm though.
Nope, doesn't work. Thanks sirbradenwalker!