Missing in Action (Story Mission)
Speak with Eli after completing The World is Weak to launch this one.
You'll need to free some hostages from the Whitetail Park Visitor Center. If you approach from the south cliffs, you'll get a good vantage on the area.
Scan carefully, then move in and take out the near sentries.
The first hostage is on the balcony of this westmost building.
The second is inside, being personally coached by a hostile.
Right by them is one of the Cheeseburger bobbleheads.
Set your sights on the main building downslope, and start eliminating lone enemies.
With the middle building balcony cleared, move down again, and use the gaps in the stone railing to clear the parking lot unseen.
Nip down and free the hostage kneeling in the parking lot.
The last hostage is inside the Visitor Center itself.
You'll get a call about even more hostages, but you may want to linger a moment to snag the fishing mag on the counter for Rainbow Trout locations.
Smiley's lighter is also on a bookshelf here.
Follow your marker up the Hawkeye Tunnel. You get a spiel over your radio about the front being crazy and the top being smart, but the front is actually the easier way to go. Start sniping into the tunnel from a distance, and keep picking off hostiles as they come forward to check out the commotion.
Just take it slow, headshot by headshot, and by the time you do reach the hostages, they'll be completely unguarded.
Free them to complete the mission.