The Arlington Cemetery Ghost is a myth in Fallout 3.
The ghost is located in the Arlington Cemetery and house. It is said that the myth started out in internet forums as simply as a rumour.
The main reason for this myth starting is likely the haunting nature of the location; it's a graveyard. Another reason is the appearance of dust that moves across the cemetery at random points of time. The dust randomly appears and disappears which usually creeps players out, many believing it to be a spirit following them. Also, some investigations have found Mister Crowley running through the graveyard. What's strange about this is that he usually resides in Underworld which is on the other side of the Potomac, which would mean he will have had to swim across to get there. The investigator believes he may be what players mistake for a ghost.
In the graveyard, it is also believed that whispering similar to the Goodsprings Cemetery can be heard.