It's a crisp, early October weekend, and business is slowing down as fall descends at the Sherlock Holmes Bookshop and Emporium and adjacent Mrs. Hudson's Tea Room. Wealthy philanthropist and prominent Sherlockian David Masterson has rented Suffolk Gardens House, where he plans to entertain his friends in a traditional English country house weekend.

As the chosen caterers, Jayne Wilson and Gemma Doyle get to work preparing lavish meals and setting up Sherlockian books and props for entertainment. Meanwhile, police detective Ryan Ashburton has taken time away from his duties to assist in the kitchen. It quickly becomes apparent that David's guests don't like each other--or their host. Plus, some of them aren't even acquainted with the adventures of the Great Detective.

Before Gemma can ponder their relationships a poisoned dart sails through the window of the library, presenting Gemma Doyle with a three-book problem.