Traveling through the Glowing Sea is an arduous task, as the radiation levels are persistent, and outright deadly in many areas. Having equipment and medical supplies at hand to deal with radiation is necessary in order to reach the cave system that Virgil is hiding within.
After stocking up on supplies for dealing with radiation, which may or may not include the use of power armor, the Sole Survivor will need to first travel to a settlement called the Crater of Atom, in which the leader of the settlement will reveal that her people have dealt with Virgil, who has traded with their group a few times in the past, but he is not living with them, as he wishes to be alone. The radiation levels are unusually low around the Crater, and in some areas, completely absent.
After convincing her to give up Virgil's location, she will direct the Sole Survivor to a nearby cave, which is currently being guarded by a deathclaw that had recently moved into the area, which must be killed or sneaked past in order to gain access to the rocky cave.
Upon meeting Virgil, who is seen to now be a super mutant, he will reveal to the Sole Survivor that the only way he will help, is if they retrieve a serum for him that he was forced to leave behind at the Institute.
After agreeing to Virgil's terms, he will reveal that the only sensible way into the Institute, is to kill an Institute courser, as their brain chips utilize encrypted code that the Institute uses to teleport them in and out of the Institute.
Once this quest has been completed, Virgil will expect the player to deliver his experimental serum once the Sole Survivor completes their maiden voyage to the Institute. Should they return to Virgil without the experimental serum, or should they continue working for the Institute before delivering the experimental serum, Virgil will become hostile upon returning to him.
Find Virgil in the Glowing Sea
I need to find Virgil, the escaped Institute scientist, somewhere in the Glowing Sea and hope that he can help me reach the Institute.