Look for the buildings on the hill side, and you'll find Mother Isolde who you can speak with. It should lead you to the edge of the Glowing Sea, and then on to the Crater of Atom. Fast travel to the nearest location you have to the Glowing Sea, and then begin heading southwest towards the map marker. I'd recommend bringing your power armor, or if you plan to avoid combat, a protective hazmat suit. Virgil's last known location was deep in the Glowing Sea, a highly irradiated wasteland to the southwest. We're returning to the main story now with The Glowing Sea.
