Medico-legal practice is largely concerned with crimes against the person, the details of which are often sordid, gruesome and unpleasant. Hence the curious and romantic case of the Blue Scarab (though really outside our specialty) came as somewhat of a relief. But to me it is of interest principally as illustrating two of those remarkable gifts which made my friend, Thorndyke, unique as an investigator: his uncanny power of picking out the one essential fact at a glance, and his capacity to produce, when required, inexhaustible stores of unexpected knowledge of the most out-of-the-way subjects. It was late in the afternoon when Mr. James Blowgrave arrived, by appointment, at our chambers, accompanied by his daughter, a rather strikingly pretty girl of about twenty-two; and when we had mutually introduced ourselves, the consultation began without preamble. “I didn’t give any details in my letter to you,” said Mr. Blowgrave. “I thought it better not to, for fear you might decline the case. It is really a matter of a robbery, but not quite an ordinary robbery. There are some unusual and rather mysterious features in the case. And as the police hold out very little hope, I have come to ask if you will give me your opinion on the case and perhaps look into it for me. But first I had better tell you how the affair happened. “The robbery occurred just a fortnight ago, about half-past nine o’clock in the evening. I was sitting in my study with my daughter, looking over some things that I had taken from a small deed-box, when a servant rushed in to tell us that one of the outbuildings was on fire. Now my study opens by a French window on the garden at the back, and, as the outbuilding was in a meadow at the side of the garden, I went out that way, leaving the French window open; but before going I hastily put the things back in the deed-box and locked it. “The building—which I used partly as a lumber store and partly as a workshop—was well alight and the whole household was already on the spot, the boy working the pump and the two maids carrying the buckets and throwing water on the fire. My daughter and I joined the party and helped to carry the buckets and take out what goods we could reach from the burning building. But it was nearly half an hour before we got the fire completely extinguished, and then my daughter and I went to our rooms to wash and tidy ourselves up. We returned to the study together, and when I had shut the French window my daughter proposed that we should resume our interrupted occupation. Thereupon I took out of my pocket the key of the deed-box and turned to the cabinet on which the box always stood. “But there was no deed-box there! “For a moment I thought I must have moved it, and cast my eyes round the room in search of it. But it was nowhere to be seen, and a moment’s reflection reminded me that I had left it in its usual place. The only possible conclusion was that during our absence at the fire, somebody must have come in by the window and taken it. And it looked as if that somebody had deliberately set fire to the outbuilding for the express purpose of luring us all out of the house.” “That is what the appearances suggest,” Thorndyke agreed. “Is the study window furnished with a blind or curtains?” “Curtains,” replied Mr. Blowgrave. “But they were not drawn. Any one in the garden could have seen into the room; and the garden is easily accessible to an active person who could climb over a low wall.” “So far, then,” said Thorndyke, “the robbery might be the work of a casual prowler who had got into the garden and watched you through the window, and assuming that the things you had taken from the box were of value, seized an easy opportunity to make off with them. Were the things of any considerable value?”