In the 3rd Annie Oakley Mystery, A Serial Affair, it’s 1893, the year of the World’s Fair in Chicago, Illinois. Annie Oakley, headlining star of Buffalo Bills Wild West Show and her husband/manager Frank Butler, travel with the troop to set up their show at the world’s biggest exhibition of the time. While there, Annie meets the mysterious Madame Charlotte, a fellow performer and popular spiritual medium in Chicago.
Annie is invited by successful businessman Dr. H.H. Holmes to stay at his famous hotel dubbed by locals as “The Castle.” Annie politely declines as she always prefers to stay on the grounds of the show to watch over her famous partner, Buck the Wonder Horse, but allows her assistant and several others who work for her to stay at the luxurious hotel. One by one, they turn up missing.
Annie learns from local officials that there have been other disappearances associated with the hotel. Together with Madame Charlotte, Annie and Frank help to uncover the killings committed by America’s first serial killer, Herman Webster Mudget, who used his famous hotel during the World’s Fair to lure his victims.