An agent of the Railroad, he appears at whichever settlement becomes the Mercer Safehouse upon completion of the quest. He is very jumpy and appears to have PTSD from the Switchboard incident when the Institute laid siege to the Railroad's former headquarters.
He does not count as a settler and cannot be assigned to tasks.
He will not become hostile if the player turns hostile to the Railroad.
If the Railroad is destroyed, he'll vanish from the Mercer Safehouse and later can be found in a random encounter, where he's about to be executed by a raider. He won't be hostile to the player if he's saved, and will speak his usual lines instead.