On PC, using console command prid 6b505 and then enable may force Virgil to appear in the cave.

This may be the result of having visited Virgil's cave prior to the quest. The marker for finding him points to the ground.

Upon entering the cave, Virgil is not there.

Mother Isolde is not marked as essential, so if she dies, the quest marker will be stuck on her for the remainder of the quest.

Because of the radiation level, using furniture to wait in the crater area is not possible.

Virgil will immediately turn hostile upon one's return in this case. Any defenses destroyed prior to returning to complete the quest will result in failing the quest when returning with the serum.

When entering the rocky cave be sure not to destroy any of Virgil's defenses.

He's told me that the key to teleporting into the Institute is a chip from an Institute Courser. I spoke with Virgil, an Institute scientist who willingly turned himself into a Super Mutant to escape. Watch out for yourself, as on the way there you can be attacked.

I need to find Virgil, the escaped Institute scientist, in a cave southwest of the crater in the Glowing Sea and hope that he can help me reach the Institute. Finding Virgil on the Glowing Sea Glowing Sea and start your journey towards the first marker. I need to find Virgil, the escaped Institute scientist, somewhere in the Glowing Sea and hope that he can help me reach the Institute. He requests that the Sole Survivor help him locate a serum within the Institute, in return for his knowledge. Locate the rocky cave roughly southwest of the Crater of Atom, being wary of the roaming deathclaw in the area. Answer her questions politely, and she will give directions to a rocky cave nearby. Though violence is always an option (search the area for a scrap of paper indicating a nearby cave), it is possible to lower one's weapon and speak to Mother Isolde instead. Upon entering the location, the Children's leader, Mother Isolde, will inform the Sole Survivor that they are trespassing. Upon reaching the map marker, the Sole Survivor will find themselves close to the Crater of Atom, a site holy to the Church of the Children of Atom. Expect to face deathclaws, radscorpions, feral ghouls and other irradiated wildlife. Travel to the Edge of the Glowing Sea and head southwest, following the remains of the freeway until the Pip-Boy indicates a hike off-road is in order. His last known position was deep in the most irradiated region of the Commonwealth, the Glowing Sea. Kellogg's memories and Doctor Amari's advice indicate that the Sole Survivor should locate an escaped Institute scientist, Virgil.

Find virgil in the glowing sea