The box proved to have a false bottom, under which lay the manuscript of a full-length adventure of Sherlock Holmes, in which the great detective needs all his cunning and detective powers to unravel the mysteries at Hareby Hall.
Mentioned in passing by Dr. Watson in his account of A Scandal in Bohemia, The Darlington Substitution is a tale of deceit, treachery, and murder most foul, set in the wild Border country of northern England. Holmes and Watson encounter a centuries-old legend which tells of the future extinction of an ancient noble family, and set themselves against one of the most ingenious and fiendish villains ever to cross the path of Sherlock Holmes.
Holmes and his faithful biographer come to life again in this case, following in the tradition already set in the three volumes of the "Deed Box" series of shorter Holmes adventures published by Inknbeans Press. These have been extremely favorably received by readers and reviewers, with one commenting, "I would have assumed that they were indeed previously undiscovered Doyle originals," and another, "The author has followed the approaches of the original Doyle stories to the extent that these could have been easily included in the original works".