As a thief in the night

by R. Austin Freeman

“Hence, when I came to consider Stella’s illness and noted the strong suggestion of arsenic poisoning; and when I noted the parallelism of her illness with that of Monkhouse; I naturally kept a watchful eye for a possible parallelism in the method of administering the poison. And not only did I find that parallelism; but in that very entry, I found strong confirmation of my suspicion that the candle was poisoned. You will remember that you mention the circumstance that on the night following the making of the wax mould you were quite seriously unwell. Apparently you were suffering from a slight attack of acute arsenical poisoning, due to your having inhaled some of the fumes from the burning candle.”

“Yes, I remember that,” said I. “But what is puzzling me is how the candles could have been obtained. Surely it is not possible to buy arsenical candles?”

“No,” he replied, “it is not. But it is possible to buy a candle-mould, with which it is quite easy to make them. Remember that, not so very long ago, most country people used to make their own candles, and the hinged moulds that they used are still by no means rare. You will find specimens in most local museums and in curio shops in country towns and you can often pick them up in farm-house sales. And if you have a candle-mould, the making of arsenical candles is quite a simple affair. Barbara, as we know, used to buy a particular German brand of stearine candles. All that she had to do was to melt the candles, put the separated wicks into the mould, stir some finely-powdered white arsenic into the melted wax and pour it into the mould. When the wax was cool, the mould would be opened and the candles taken out—these hinged moulds usually made about six candles at a time. Then it would be necessary to scrape off the seam left by the mould and smooth the candles to make them look like those sold in the shops.”

“It was a most diabolically ingenious scheme,” said I.

“It was,” he agreed. “The whole villainous plan was very completely conceived and most efficiently carried out. But to return to our argument. The discovery that Stella had used a special form of candle left me in very little doubt that Barbara was the poisoner and that poisoned candles had been the medium used in both crimes. For we were now out of the region of mere hypothesis. We were dealing with genuine circumstantial evidence. But that evidence was still much too largely inferential to serve as the material for a prosecution. We still needed some facts of a definite and tangible kind; and as soon as you came back from your travels on the South-Eastern Circuit, fresh facts began to accumulate. Passing over the proceedings of Wallingford and his follower and the infernal machine—all of which were encouraging, as offering corroboration, but of no immediate assistance—the first really important accretion of evidence occurred in connection with our visit to the empty house in Hilborough Square.”

“Ha!” I exclaimed. “Then you did find something significant, in spite of your pessimistic tone at the time? I may say, Thorndyke, that I had a feeling that you went to that house with the definite expectation of finding some specific thing. Was I wrong?”

“No. You were quite right. I went there with the expectation of finding one thing and a faint hope of finding another; and both the expectation and the hope were justified by the event. My main purpose in that expedition was to obtain samples of the wall-paper from Monkhouse’s room, but I thought it just possible that the soot from the bedroom chimneys might yield some information. And it did.

“To begin with the wall-paper: the condition of the room made it easy to secure specimens. I tore off about a dozen pieces and wrote a number on each, to correspond with numbers that I marked on a rough sketch-plan of the room which I drew first. My expectation was that if—as I believed—arsenical candles had been burnt in that room, arsenic would have been deposited on all the walls, but in varying amounts, proportionate to the distance of the wall from the candle. The loose piece of paper on the wall by the bed was, of course, the real touchstone of the case, for if there were no arsenic in it, the theory of the arsenical candle would hardly be tenable. I therefore took the extra precaution of writing a full description of its position on the back of the piece and deposited it for greater safety in my letter-case.

“As soon as I reached home that day I spread out the torn fragment on the wide stage of a culture microscope and examined its outer surface with a strong top light. And the very first glance settled the question. The whole surface was spangled over with minute crystals, many of them hardly a ten-thousandth of an inch in diameter, sparkling in the strong light like diamonds and perfectly unmistakable; the characteristic octahedral crystals of arsenious acid.

“But distinctive as they were, I took nothing for granted. Snipping off a good-sized piece of the paper, I submitted it to the Marsh-Berzelius test and got a very pronounced ‘arsenical mirror,’ which put the matter beyond any possible doubt or question. I may add that I tested all the other pieces and got an arsenic reaction from them all, varying, roughly, according to their distance from the table on which the candle stood.