Virgil's letter is a paper note in Fallout 4.
Location[]
Given by Brian Virgil to the Sole Survivor if he is cured.
Transcript[]
Doctor,
Our mutual friend informed me of your concern for my health. With the aid of <Alias.PronounPosObj=Player>, I was able to secure an antidote for my condition, and am pleased to report that I have made a full recovery.
Although our circumstances have changed, I hope we might someday be able to collaborate on our research once again. Until then, my regards.
Sincerely,
V.