‘You silenced McParland and removed any trace of his identity, missing only the cigarette case. And with him gone, there was nothing to stand in the way of the rest of your scheme.’
‘There is more?’ Carstairs rasped. All the blood had left his face and I thought he might be about to faint.
‘Indeed so, Mr Carstairs.’ Holmes turned back to the wife. ‘The cold-blooded marriage that you had arranged for yourself was only the means to an end. It was your intention to kill Edmund’s family one at a time: his mother, his sister and then he. At the end of it, you would inherit everything that had been his. This house, the money, the art… all of it would be yours. It is hard to imagine the hatred that must have been driving you forward, the relish with which you went about your task.’
‘It has been a pleasure, Mr Holmes. I have enjoyed every minute of it.’
‘My mother?’ Carstairs gasped the two words.
‘The most likely explanation was the one you first suggested to me, that the gas fire in her bedroom blew out. But it was not one that stood up to scrutiny. For your manservant, Kirby, told us that he blamed himself for the death as he had stopped up every crack and crevice in the room. Your mother disliked draughts so it was impossible that a draught could have blown out the fire. Your sister, however, had come to another conclusion. She believed that the late Mrs Carstairs had taken her own life, so distraught was she at your marriage. But as much as Eliza loathed your new wife and instinctively knew her to be dissembling, even she was unable to arrive at the truth, which is that Catherine Carstairs entered the room and deliberately blew out the flame, leaving the old lady to perish. There could be no survivors, you see. For the property to be hers, everyone had to die.’
‘And Eliza?’
‘Your sister is being slowly poisoned.’
‘But that’s impossible, Mr Holmes. I told you—’
‘You told me that you have carefully examined everything she has eaten, which only suggests to me that she is being poisoned in another way. The answer, Mr Carstairs, is the bath. Your sister insists on bathing regularly and uses strong, lavender bath salts. I must confess that this is a most novel way of administering poison, and I am frankly surprised that it has been so effective, but I would say that a small measure of aconitine has been added, regularly, to the bath salts. It has entered Miss Carstairs’s system through her skin and also, I would imagine, through the moisture and the fumes which she has, of necessity, absorbed. Aconitine is a highly toxic alkaloid which is soluable in water and which would have killed your sister instantly if a large dose had been used. Instead, you have noted this slow but remorseless decline. It is a striking and innovative method of murder, Mrs Carstairs, and one which I am sure will be added to the annals of crime. It was also quite daring of you, incidentally, to visit my colleague while I was incarcerated, although you naturally pretended you knew nothing of that. It doubtless persuaded your husband of your devotion to your sister-in-law while, in fact, you were actually laughing at them both.’
‘You devil!’ Carstairs twisted away from her in horror. ‘How could you? How could anyone?’
‘Mr Holmes is right, Edmund,’ his wife returned and I noticed that her voice had changed. It was harder, the Irish accent now prominent. ‘I would have put all of you in your graves. First your mother. Then Eliza. And you have no idea what I was planning for you!’ She turned to Holmes. ‘And what now, clever Mr Holmes? Do you have a policeman waiting outside? Should I go upstairs and pack a few things?’
‘There is indeed a policeman waiting, Mrs Carstairs. But I have not finished yet.’ Holmes drew himself up and I saw a coldness and a vengefulness in his eyes that went beyond anything I had ever seen before. He was a judge about to deliver sentence, an executioner opening the trapdoor. A certain chill had entered the room. A month from now, Ridgeway Hall would be empty, unoccupied — and am I too fanciful to suggest that something of its fate was already being whispered, that somehow the house already knew? ‘There is still the death of the child, Ross, to be accounted for.’
Mrs Carstairs burst out laughing. ‘I know nothing about Ross,’ she said. ‘You have been very bright, Mr Holmes. But now you go beyond yourself.’
‘It is no longer you I am addressing, Mrs Carstairs,’ Holmes replied and turned instead to her husband. ‘My investigation into your affairs took an unexpected turn on the night that Ross was murdered, Mr Carstairs, and that is not a word I use often, for it is my habit to expect everything. Every crime that I have ever investigated has had what you might call a narrative flow — it is this invisible thread that my friend, Dr Watson, has always unerringly identified. It is what has made him such an excellent chronicler of my work. But I have been aware that this time I have been diverted. I was following one line of investigation and it took me, suddenly and quite accidentally, onto another. From the moment I arrived at Mrs Oldmore’s Private Hotel, I had left Boston and the Flat Cap Gang behind me. Instead, I was moving in a new direction and one that would eventually take me to the unveiling of a crime more unpleasant than any I had ever encountered.’
Carstairs flinched when he heard this. His wife was regarding him curiously.
‘Let us go back to that night, for you, of course, were with me. I knew very little about Ross, except that he was one of the band of street urchins that I have affectionately named the Baker Street Irregulars and who have helped me from time to time. They have been of use to me and I have recompensed them. It seemed a harmless arrangement, at least until now. Ross was left to watch the hotel while his companion, Wiggins, came for me. We drove, the four of us — you, me, Watson and Wiggins — over to Blackfriars. Ross saw us. And at once I perceived that the boy was terrified. He asked who we were, who you were. Watson attempted to reassure him and, in doing so, both named you and gave the boy your address. That, I rather fear, was to be the death of him — though do not blame yourself, Watson, for the mistake was equally mine.
‘I had assumed that Ross was frightened because of what he had seen at the hotel. It was a natural assumption to make for, as things turned out, a murder had taken place. I was convinced that he must have seen the killer and, for reasons of his own, had decided to keep silent. But I was wrong. What had frightened and amazed the boy was nothing to do with it at all. It was the sight of you, Mr Carstairs. Ross was determined to know who you were and where he could find you because he recognised you. God knows what you had done to that child, and even now I refuse even to consider it. But the two of you had met at the House of Silk.’
Another dreadful silence.
‘What is the House of Silk?’ Catherine Carstairs asked.
‘I will not answer your question, Mrs Carstairs. Nor do I need to address myself to you again except to say this: your entire scheme, this marriage of yours, would only have worked with a certain sort of man — one who wanted a wife to spite his family, to give him a certain standing in society, not for reasons of love or affection. As you put it so delicately yourself, you knew him for what he was. I myself wondered exactly what sort of creature I was dealing with on the very first day that we met for it always fascinates me to meet a man who tells me he is late for a Wagner opera on an evening when no Wagner is being played in town.
‘Ross recognised you, Mr Carstairs. It was the very worst thing that could have happened, for I can imagine that anonymity was the watchword at the House of Silk. You came in the night, you did what you had to do, and you left. Ross was, in all this, the victim. But he was also old beyond his years and poverty and desperation had driven him inexorably to crime. He had already stolen a gold pocket watch from one of the men who had preyed on him. As soon as he got over the shock of encountering you, he must have seen the possibilities of considerably more. Certainly, that is what he told his friend, Wiggins. Did he visit you the next day? Did he threaten to expose you if you did not pay him a fortune? Or had you already scuttled off to Charles Fitzsimmons and his gang of thugs and demanded that they take care of the situation?’