One murder. One victim. 47,000 suspects.

Mayfair, the morning after the dinner. Lady Constance Cavendish, seventy-three, the last of her line, lies slumped over the writing desk in the library at Cavendish House. Inspector Hartmann hands you her household guest book: forty-six years of names, 47,000 first names, seventeen clues, one killer.

Edinburgh, the morning the Festival opens. Harriet MacKenzie, sixty-eight, the last of two generations of booksellers on the Royal Mile, lies slumped over the back-room desk between the Walter Scott collection and the cabinet of first editions. Inspector Hartmann opens her order book: ninety-eight years of customer names, 47,000 first names, seventeen clues, one killer.

Oxford, the morning after high table. Sir Edmund Hartwell, seventy-eight, President of Magdalen College since 2004, lies slumped in the wing chair beneath the portrait of Cardinal Wolsey in the President's Lodgings. Inspector Hartmann hands you the Lodgings Day Book: twenty-two years of Magdalen guests, 47,000 first names, seventeen clues, one killer.

Bath, the Saturday of the Jane Austen Festival, 5:38 PM. Lady Imogen Pendarvis, seventy-one, retired Keeper of Costume and Honorary Archivist of the benefactor roll at the Holburne Museum, lies at her writing desk on the first floor of No. 11 The Circus. Inspector Hartmann opens the Holburne benefactor roll: 130 years of givers and lenders, 47,000 first names, seventeen clues, one killer.

York, the Saturday of Illuminating-York, 6:14 PM. Miss Edith Rowntree-Pearce, sixty-nine, retired Senior Archivist of the Borthwick Industrial Records and honorary editor of the Standing Committee, lies in the hallway of her terrace at 42 Bishophill Senior. Inspector Hartmann opens the Borthwick Industrial Records cross-reference: a century and a half of York chocolate-firm minute-books, 47,000 first names, seventeen clues, one killer.