Long thought lost, Sherlock Holmes' monograph on the Posthumous Motets of Orlandus Lassus can at last be printed. The musicologist and Sherlockian, Michael Procter, discovered Holmes' notes for the essay in the Bavarian State Library; in this booklet he describes his discovery and introduces and annotates Holmes' study, with essays on Lassus & Melancholy, Holmes & Depression and references to Holmes' life and to the cases of the great detective.