Sir Arthur Conan Doyle is an Irishman; and in his own country, within my own memory, there occurred a staggering and almost incredible crime, or series of crimes, which were worthier than anything in the world of the attention of Sherlock Holmes in fiction, or Conan Doyle in reality. It always will be a tribute to the author of _Sherlock Holmes_ that he did, about the same time, do such good work in reality. He made an admirable plea for Adolf Beck and Oscar Slater; he was also connected, I remember, with the reversal of a miscarriage of justice in a case of cattle-mutilation. And all this, while altogether to his credit, makes it seem all the more strange that his talents could not be used for, and in, his own home and native country, in a mystery that had the dimensions of a monstrosity, and which did involve, if I remember right, a question of cattle-maiming. Anyhow, it was concerned with moonlighters and the charges made against them, such as the common one of cutting off the tails of cows. I can imagine Sherlock Holmes on such a quest, keen-eyed and relentless, finding the cloven hoof of some sinister and suspected cow. I can imagine Dr Watson, like the cow’s tail, always behind. I can imagine Sherlock Holmes remarking, in a light allusive fashion, that he himself had written a little monograph on the subject of cows’ tails; with diagrams and tables solving the great traditional problem of how many cows’ tails would reach the moon; a subject of extraordinary interest to moonlighters. And I can still more easily imagine him saying afterwards, having resumed the pipe and dressing-gown of Baker Street, ‘A remarkable little problem, Watson. In some of its features it was perhaps more singular than any you have been good enough to report. I do not think that even the Tooting Trouser-Stretching Mystery, or the singular little affair of the Radium Toothpick, offered more strange and sensational developments.’ For if the celebrated pair had really tracked out the Irish crime I have in mind, they would have found a story which, considered merely as a detective story, is by far the most dramatic and dreadful of modern times. Like nearly all such sensational stories, it traced the crime to somebody far higher in station and responsibility than any of those suspected. Like many of the most sensational of them, it actually traced the crime to the detective who was investigating it. For if they had really crawled about with a magnifying glass, studying the supposed footprints of the peasants incriminated, they would have found they were made by the boots of the policeman. And the boots of a policeman, one feels, are things that even Watson might recognise.