Veluis is correct, I did this tonite. The "Hidden Path" you need to find is in the small ravine S of the Den area; it loops around E to W. At the W end (SW of your starting point, just like he quest says), the trail is up the hill behind the last Lazy Peon. Follow it to the end and use the Sapta in front of the runestone, then talk to the big stone dude.
Just don't fall off the path and into The Barrens, because it's not a good place to be at 4th level. Go ahead and inch up to the edge for the free XPs, tho... =]