‘Having gathered these facts, Watson, I smoked several pipes over them, trying to separate those which were crucial from others which were merely incidental. There could be no question that the most distinctive and suggestive point in the case was the singular disappearance of the door key. A most careful search had failed to discover it in the room. Therefore, it must have been taken from it. But neither the Colonel nor the Colonel’s wife could have taken it. That was perfectly clear. Therefore a third person must have entered the room. And that third person could only have come in through the window. It seemed to me that a careful examination of the room and the lawn might possibly reveal some traces of this mysterious individual. You know my methods, Watson. There was not one of them which I did not apply to the inquiry. And it ended by my discovering traces, but very different ones from those which I had expected. There had been a man in the room, and he had crossed the lawn coming from the road. I was able to obtain five very clear impressions of his footmarks—one on the roadway itself, at the point where he had climbed the low wall, two on the lawn, and two very faint ones upon the stained boards near the window where he had entered. He had apparently rushed across the lawn, for his toe marks were much deeper that his heels. But it was not the man who surprised me. It was his companion.’

‘His companion!’

Holmes pulled a large sheet of tissue paper out of his pocket and carefully unfolded it upon his knee.

‘What do you make of that?’ he asked.

The paper was covered with tracings of the footmarks of some small animal. It had five well-marked footpads, an indication of long nails, and the whole print might be nearly as large as a dessert spoon.

‘It’s a dog,’ said I.

‘Did you ever hear of a dog running up a curtain? I found distinct traces that this creature had done so.’

‘A monkey, then?’

‘But it is not the print of a monkey.’

‘What can it be, then?’

‘Neither dog, nor cat, nor monkey, nor any creature that we are familiar with. I have tried to reconstruct it from the measurements. Here are four prints where the beast has been standing motionless. You see that it is no less than fifteen inches from fore foot to hind. Add to that the length of neck and head, and you get a creature not much less than two feet long—probably more if there is any tail. But now observe this other measurement. The animal has been moving, and we have the length of its stride. In each case it is only about three inches. You have an indication, you see, of a long body with very short legs attached to it. It has not been considerate enough to leave any of its hair behind it. But its general shape must be what I have indicated, and it can run up a curtain and is carnivorous.’

‘How do you deduce that?’

‘Because it ran up the curtain. A canary’s cage was hanging in the window, and its aim seems to have been to get at the bird.’

‘Then what was the beast?’

‘Ah, if I could give it a name it might go a long way towards solving the case. On the whole it was probably some creature of the weasel or stoat tribe—and yet it is larger than any of these that I have seen.’

‘But what had it to do with the crime?’