A team up with Baranor, who's wandered awfully far from home. Follow the marker to find him on the trail of a Warchief's bodyguards.
You'll get a brief tutorial on the connection between warchiefs and bodyguards, then the hunt is on. During this section you can use Baranor as a long-distance stealth kill. Note that orcs haven't gotten any smarter, so you can usually score a stealth kill even if the enemy is facing you (though nearby orcs will likely be alerted. In anycase, you get a bonus for racking up at least 5 kills this way, so use the technique whenever possible.
Kill your way to the objective marker to reveal another glowing footprint trail. Don't even need to be Wraithed to see it.
The trail leads to a captain. You can make things easier on yourself by stealth killing the many orcs on the periphery first, but even if you don't, Baranor makes for reasonably good backup. With Cel pitching in, you're practically the Three Musketeers.
Finish off the captain to clear a path to the warchief, and end the mission.