Anchored by ABC News' Amy Robach, the program is scheduled to air Dec. 26.
"You don't have to be a 'Downton Abbey' fan to love it when the 'Mysteries of the Castle' are revealed on ABC," the network said in a release Thursday.
"How has the relationship between owners and the help changed over the years? How has the show's pop hit status affected the real life abbey? Did historical events inspire story lines in the series? The special answers these questions and also introduces viewers to owners of other estates putting a modern twist to British aristocracy," ABC said. "It's a no holds barred look at what it means today to be British, rich and titled."
Season 4 of Downton Abbey is now airing on British television. It will premiere in the United States on PBS Jan. 5.