cause of it. If not, this letter will enlighten you, so that you can destroy the said cause and sleep the sleep of the innocent.
"Consider the humble pentagram. It's become a jolly little figure of fun now—good luck, and all that sort of thing. You might get it in the form of a lucky charm from a Christmas cracker or see a dozen of it representing stars in the illustrations to children's fairy story books.
"Business men who like playing at secret societies (which are also good for business) use it for a secret recognition symbol between one member and another. They copied that trick from the Pythagoreans. But the Pythagoreans were alive to the dread secret they shared, and which they kept from the ordinary people. Yet even these philosopher-geometricians were a bit astray upon one point.
"Because they traced manifestations to the presence of a pentagram of a certain size and shape, they thought that the secret lay in that certain size and shape. And certainly the same effects were brought about through using exact duplicates of that original pentagram.
"But the whole secret really lies in just one triangle of that figure. The surface size is irrelevant, and the rest of the pentagram frame redundant. It's the angles of that one triangle which are important. Fashion a triangle with its three angles of sizes I could give you (though an error amounting to a second will suffice to make it impotent) and you will have a triangle of terror indeed.
"I'll tell you that one angle is 36° 47' 29" if you want to play games with trial and error. When you hit upon the right one and leave it about, you'll start seeing things sooner or later. But your chances are small. It is not an isosceles triangle, but a scalene. The original pentagram was a very rough effort, far from symmetrical, and only by a fluke did it contain this dangerous triangle.
"How did I discover all this? It began with my investigation of the haunting of a cottage in Norfolk. I connected the phenomena with a small glass prism which had been lying about the place (the former occupant was a spectroscopist—until he went mad and was put away). On a couple of occasions when the spooks were about to appear, I noticed that this prism took on a palely translucent quality of green. Proceeding according to scientific method, I found that the cottage was not haunted if the prism was taken away from it. But the vicinity of the prism was, wherever one took it. I had a rather unpleasant time discovering that—I must tell you about it sometime.
"Unfortunately, I dropped the prism one day and broke a corner off. And it was never the same again. It became just another piece of glass. But I had taken exact measurements of it, and I kept them.
"Years later, I traced, by exhaustive trial and error, the cause of another haunting—in a residential house on Putney Common—to the presence of (of all things!) a paper-fastener. A triangular one. I took careful measurements of this, and compared them with the dimensions of that remembered prism. I knew I had hit upon something when I found that its angles—though not the area enclosed by them—corresponded absolutely exactly with the angles of one of the (naturally) triangular ends of the prism, the end I had broken.
"I'm afraid I didn't keep my evidence long. I was so troubled by 'dreams and visions' as long as it was in my possession that I was finally driven to bending it out of shape. That made it harmless. A simple little action like that.
"But I found plenty of confirmatory evidence. That haunted riverside bungalow at Teddington: I removed and destroyed one of those common triangular shelf brackets, and got the credit for exorcising the spirits! Do you know why Burlham Rectory is still known as 'the most haunted house in Britain'? Because I couldn't get permission to attack a beam completing a triangle of one of the gables!
"I tell you, you've only got to look around any of these 'haunted' houses, and know what you're looking for, and you'll find the cause of the trouble sooner or later. It may be a fortuitous triangle of scratches on the
