The Glowing Sea

The Glowing Sea is a main story quest in Fallout 4.

Quick walkthrough

 * 1) Find Virgil in the Glowing Sea.

Detailed walkthrough
Kellogg's memories and Doctor Amari's advice indicate one should locate an escaped Institute scientist. His last known position was deep in the most irradiated region of the Commonwealth—the Glowing Sea.

Commence the long trek southwest, following the remains of the freeway until your Pip-Boy indicates a hike off-road is in order. Expect to face radscorpions, feral ghouls, and other irradiated wildlife. When reaching the map marker, the player character is close to the Crater of the Atom.

When entering the location of a strange cult, led by Mother Isolde, the Sole Survivor is actually trespassing. Though violence is always an option (search the area of a scrap of paper indicating a nearby cave), one can lower the weapon and speak to Mother Isolde. Answer her politely. She directs to a nearby cave.

Locate the rocky cave roughly southwest of the Crater of the Atom. Watch for, or sneak past, the roaming deathclaw.

The Sole Survivor ll find Virgil inside this cave. He requests to help him locate a serum within the Institute in return for his knowledge.