Ghoul guard

Ghoul guards are seen guarding the Museum Authority Building from people looking to learn the secret of aqua cura. It is also explained in the note Griffon's bottling instructions that they are the ones who pick up the aqua pura deliveries from the Brotherhood of Steel and switch it with ordinary irradiated water to be sold as aqua cura.

Quests
The Amazing Aqua Cura!

Appearances
Ghoul guards appear in the Fallout 3 add-on Broken Steel.