I had to make several attempts before I got the various numbers to my liking. For instance, if the chances that Annie had information about the Chinese poison were to be represented by the figure three, was it just that the figure two should be set down against the cook? Or should they not be five and four respectively? Then I had to look back through my notes again to see what I had written down against the others, and perhaps alter all the figures in the column, before I reached what I considered was an estimate that was fair and just to all of us.

I, of course, appreciated at once that it was only a very rough measure of possibilities, that it might give me the wildest of results, and that it was entirely unjust to count up the totals in the way I had done. But it did compel me to make detailed comparisons. It did give me some sort of an index figure against each member of the party. It showed me immediately that The Tundish and Ethel stood in a category apart from the rest of us in that they had a score of five or over under every head in the table. I was again surprised to notice how heavily Ethel was involved. No wonder Allport had been so persistent in his questions. Of the rest of us, Miss Summerson, Annie, cook and myself, were all roughly alike with a score lying between twenty and thirty, and we were alike too in that we had no score at all under the important heading “Motive.” Margaret, Kenneth and Ralph were, all three, practically equal at the bottom, but for each of them there was a conceivable motive.

I must have sat pondering over my notes for more than an hour, and it amused me to wonder what the clever little Allport would have said of my efforts. Time had passed almost unheeded, and when the cathedral clock registered a deep-noted one, I was surprised to find that it was the half-hour after midnight instead of half past eleven as I had expected. The cat had been seated, blissfully happy, on my knee while I wrote, and perching him on my shoulder again, I got up with a sigh, my mind quite made up that The Tundish must be guilty. No other explanation seemed capable of being twisted and molded to fit the whole of the facts.

The windows were still open and I went round the room shutting them one by one, At the big French window I stood for a time looking out on the moonlit garden. Then I decided to go out and see if I could find any ladder near the surgery wing that might have been used for getting on to the flat-roof top. I would finish my job. I opened the window and stood for a time on the narrow asphalt path that ran round the back of the house.

It was almost painfully beautiful, and I remember that as I stood looking at the quiet garden scene, I fell to wondering what quality it held that filled me with such unutterable sadness. Not a leaf was moving. A motorcycle passed along the road at the front of the house with a sudden roar—a splash in the pool of silence. Then the ripples died away and all was glassy calm once more.

From the high cathedral tower what a view there must be on a night like this—first the houses of the city huddled round the base of the hill, a study in shady blacks and steely blues as the moon’s pure light picked out this old house in light and shade and played on the sloping roof of that—then for miles around, the undulating countryside, billowy sea of misty gray and blue.

And in all the scene, I thought, city and countryside alike, there could be no roof that sheltered such unhappiness, as the roof of the old red Georgian house underneath whose shadow I stood.

The cat still cuddling comfortably up against my neck, I walked across the lawn toward the surgery wing. The end away from the house lay deep in the shade, but there, plain enough, slung across two stout iron hooks, was a short wooden ladder. It was short, but, I calculated, long enough to allow of any fairly active person reaching the roof and gaining access to Stella’s bedroom window.

I looked up at the house. I could just make out the white framed windows from the surrounding shadows. The moon rode clear between the chimneys and over the old red roof. Then as I watched I saw a light shine in the window that lights the stairs between the first and second floors. Just a faint but steady glow. It came and went again as I stood wondering what on earth it could be.

The light might have come, I decided, from either the first or the second landing, but it was not the light I should have seen had any one switched on either of the landing lights. It was not nearly bright enough for that. Had some one struck a match? No, for that it was too equal and steady. Or some one perhaps had opened the door of a lighted room, and the reflected light had given that momentary steady glow to the staircase window? No, and that didn’t quite meet the case either, I thought. Had it been the light from an open door, surely it would have faded away more gradually as the door was closed? Quickly, perhaps, but not with a sudden jerk like the light I had seen at the window. That had gone out with a click. A click! Yes, that was it. Some one had been using an electric flash-light on one of the landings.