“The summer had passed and autumn was well advanced when, one day, the morning post brought a small package for Professor Palfreyman as we were seated at the breakfast table. This was just two or three weeks ago, in the middle of October.

“‘It is probably one of those Etruscan specimens I have been after for a while,’ said he in an enthusiastic tone as he cut the string and unwrapped the parcel. ‘Let us see!’

“Within the brown paper was a stout cardboard box, and within the box was loose straw and similar packaging material. Professor Palfreyman thrust his hand into this and withdrew a wide, flat object, wrapped in tissue paper, which I thought might be a tile of some kind. He laid it on the table, and I stood up and came round behind his chair to get a better look at it. As he unwrapped the tissue paper, I saw that it was indeed a glazed tile, about four or five inches square. In colour, it was a creamy-white, and on it, in shallow relief, was depicted a most beautiful smiling female face.

“‘Oh, how lovely!’ I cried aloud, but even as I did so, I knew that something was wrong. With a strange, inarticulate cry, Professor Palfreyman pushed his chair back from the table and staggered to his feet. For a moment he stood there, swaying unsteadily, his eyes staring wildly, his mouth agape, then, abruptly, he pitched forward senseless upon the breakfast table. I called Mrs Wheeler, and between us we managed to lay the professor on the hearthrug, with a blanket over him and a cushion under his head. Mrs Wheeler brought in some fresh strong coffee a few minutes later, and when he stirred, I got him to take a sip. Presently he sat up, but as he did so, he groaned and clutched his head.

“‘Oh, my head!’ said he. ‘What happened?’

“Then, as he remembered, a grim expression came over his face. He stood up unsteadily, then, without another word, picked the tile up from the table and walked out of the house with it. A few moments later, I heard a noise outside, and when I looked out I saw that he had taken a hammer from the tool shed and, with a series of violent blows, was smashing the tile up on the ground. He then picked up all the broken pieces, placed them in a small pail, and carried them off down the back garden and into the woods. When he returned to the house ten minutes later, he made no reference to what had happened. He simply asked me if I would be so good as to clear the debris from the breakfast table, then disappeared into his study to work on his manuscript.”

“One moment,” said Holmes, holding his hand up to interrupt Miss Calloway’s narrative. “When you cleared away the wrapping paper and other materials that had enclosed the tile, did you observe where it had come from, or where it had been posted?”

Miss Calloway shook her head. “It was the first thing that occurred to me,” she replied, “but there was no label or other identifying mark anywhere on the package. The postmark was smudged, and all I could see of that was that it had been posted somewhere in London. I also went most carefully through the packing materials, to see if there was a note anywhere in it that we had missed, but there was not.”

“What became of this material?”

“I burnt it all in the incinerator in the garden.”

“Very well. Pray continue with your account.”

“The professor has never referred to this incident since, and there is something in his manner that has prevented my asking him about it. Of course, I have often thought about it and wondered what it might mean, but could make nothing of it. But that it had had a profound effect upon the professor I could not doubt. The following day, I carried some papers into his study and found that he was not at his desk as usual, but had pulled out an old tin trunk from under a chest of drawers and was rooting around in it. Presently, he found what he was looking for and held it up, and I saw that it was a very small revolver. I was aware that he possessed such a weapon, for he had often told me how some of his archaeological expeditions in years gone by had taken him into wild and dangerous places, in which possession of a pistol might be the difference between life and death, but I had never seen it before. He then spent the next hour cleaning and oiling this revolver and, having found an old box of cartridges, spent half the afternoon in target practice at the bottom of the garden. When I went out to ask him what he was doing, he answered me in a grave tone.

“‘There are circumstances, Georgina – and one must recognize them when they arise – in which one must be on one’s guard at all times.’ He then offered to teach me how to use the little pistol effectively, but I declined the offer.

“A few days after this, I had been up to town on various errands, and returned by the late afternoon train. It was a cold, foggy day, and the light had almost gone by the time the train reached Beckenham. There were few people about as I left the station, and by the time I had been walking for two minutes, I was all alone on the road. This did not particularly concern me: I had walked alone down that quiet and remote road so many times in the last year that I felt I could have done it with my eyes closed; but as the grey, drifting fog closed in around me, it did feel uncommonly cold and lonely. I could see only a few feet in front of me, and practically nothing on either side. I had been walking for perhaps ten or twelve minutes, and had turned down the long narrow lane that leads towards Bluebell Cottage, when I had the distinct impression that there was someone else on the road, somewhere behind me. Of course, the fog creates strange echoes of one’s own footsteps, in addition to the constant dripping noises among the trees, but on this occasion the impression was so strong that I stopped and turned. There was nothing to be seen there but a white wall of fog, and the other footsteps I’d thought I had heard had stopped when my own did. I turned again and resumed my progress through the fog, but this time at a brisker rate. Then I had the impression that someone or something was in the wood at the side of the road, keeping step with me, and I hurried forward. But the other steps, and the rustling in the trees, at once increased in pace, too, and I began to run as fast as I could. By the time I reached the garden gate of Bluebell Cottage and could make out the hall light shining through the fanlight over the door, I was almost completely out of breath. However, relieved though I was, I did not pause, but pushed open the gate, ran up the short path and hurried in at the front door.

“As I took my coat off, I put my head into Professor Palfreyman’s study to tell him I was home, but saw to my surprise that he was not there. I then went through to the kitchen, where Mrs Wheeler was making pastry, and asked her if she knew where the professor was. She said that she thought she had heard him go out to the garden half an hour previously and had not seen him since.

“‘But it’s quite dark now,’ I protested. ‘What is he doing in the garden in the dark?’

“Before she could answer, we heard the front door open and, looking out of the kitchen, I saw it was the professor, looking grim-faced. As he came in, I saw that he slipped his little pistol into his jacket pocket.

“‘I thought I heard someone moving about out there,’ said he in answer to my query. I suggested that it was perhaps me he had heard, as I had only recently arrived, and asked if he had been up the road at all, but he shook his head. I then ventured to suggest that we had perhaps both been mistaken, but this suggestion seemed to irritate him intensely, and I wished I had not made it. Then, as we stood there in the hall, we both heard the unmistakeable sound of footsteps on the garden path. A moment later, there came a loud rat-a-tat-tat at the doorknocker. Professor Palfreyman yanked the door open and there, blinking in the light of the hall, stood Professor Ainscow.