You can collect this mission from the Bounty Board in Overlook. Sir Hammerlock will have you searching around for the recordings of a man named Taggart who was tasked with eridicating the Stalker population in the Highlands.
- XP: 2611
- Money: $275
- Gear: Shotgun or Shield
There are two parts to this mission but neither are particularly hard or tricky once you figure them out. The first is to just kill 15 stalkers which is almost impossible not to do considering you'll basically be thoroughly searching various Stalker nests around the area. In fact, I'd nearly finished it before finding my first recording.
The second (and primary) objective is to find the audio recordings. These will be scattered around various Stalker nests in the Highlands. Stalkers like to each ECHO devices so it seems you'll have to search through their excrement to find these recordings.
There will be a few nests marked on the map and each on could potentially have a recording. If you don't find one in a particular nest, that's alright because it is possible to find multiple recordings in a single nest - I found three in one nest for instance. The key is that you need to search high and low. There will clearly be the piles on the ground that you can search through but there will also be blobs hanging from the ceilings. If you shoot or hit these, they will burst and could also have recordings in them. In fact, I had more luck with these than the piles (though they appear in both).
Unfortunately, I can't tell you exactly where the recordings will appear because it seems that the placement has been random. It can be sort of hit or miss so don't worry about it too much, just keep searching and you should have no problem finding them all before you've cleared all of the nests.
After you've done both objectives, you'll be sent to turn in the mission but you'll turn it in by finding another ECHO device in a mailbox.