Lord Ingram’s eyes gleamed. “That will not be necessary. Holmes had instructed that should the answers to both questions be yes, I may go ahead and tell you that it is Holmes’s theory that Mrs. Cousins’s suspicions got the better of her sense. More specifically, she became convinced that her maid had stolen her precious pearls and replaced them with a pair of replicas, French imitations which are said to be able to fool the eyes of an expert. To prove that it was indeed the case, she dropped the earrings into a container filled with hot vinegar—ergo the odor in her rooms—because paste pearls would not dissolve in vinegar.”
Alice gasped. “And the pearls must have dissolved, fully or partially, which proved her maid’s innocence but destroyed the expensive earrings!”
“No wonder she needed to take to her bed!” exclaimed Treadles. “And no wonder she couldn’t have her maid charged with any crime when her own stupidity was her undoing.”
“Oh but she did dismiss the poor woman without a letter of character. After seven years of service!” Alice set her hand on her husband’s sleeve. “We must find her so that I may provide a letter of character for her—and to amend for my sister-in-law’s unkindness.”
“Consider it done, my dear.” Treadles turned back to Lord Ingram. “But this Holmes fellow is marvelous.”
“Holmes’s mind has always been a thing of beauty,” said Lord Ingram with a slight smile.
Two months later, while dining out with Lord Ingram in town, Alice related a tragic but curious case that came to her via her physician, Dr. Motley, who had learned of it many years ago from a colleague. The colleague had attended a prominent family. The daughter of the house, who was about fourteen at the time, had suffered for a while from a deep melancholia. One morning, by all appearances, she passed away peacefully in her sleep. The parents, though devastated, believed it to have been an act of God, that their child was now in a much better place. The family physician, however, could not bring himself to put faith in such a fairytale.
He dared not voice his thoughts aloud to the parents, but did confide in Motley his suspicion that the girl had committed suicide, even though he couldn’t find any evidence to that effect. She had on occasion taken a sip of her mother’s laudanum to help her sleep, but the draught was always measured out carefully by the mother, drop by drop. No empty bottles of morphine or chloral lay by the girl’s bedside. No signs of suffering or struggle that would have betrayed the involvement of arsenic or cyanide. She had said good night to her parents a perfectly healthy young woman and in the morning they had found themselves sobbing over her inert body.
“Perhaps your friend Holmes can solve this terrible riddle, my lord,” Alice had said to Lord Ingram.
The next evening Inspector Treadles received a note from Lord Ingram. He had a question from Holmes. Was soda water made on the premises for the consumption of the household?
As it so happened, Alice, calling on her father, whose health was deteriorating, had run into Motley the following day. She took the opportunity to pose the question. A surprised Motley had answered in the affirmative: Yes, he believed that the staff at the house did procure canisters of liquid carbon dioxide to make soda water.
Treadles passed on the intelligence to Lord Ingram. An answer came in due time. According to Holmes, as relayed by Lord Ingram, the girl had died of self-inflicted hypercapnia. When liquid carbon dioxide evaporated, the process dramatically lowered the surrounding temperature, so that some of the liquid carbon dioxide froze into a solid—a phenomenon someone in the house might have shown her.
On the night of her death she could have replicated that process, smuggled the resulting solid pieces to her room, and then, when she was drowsy from the laudanum, set the frozen carbon dioxide on her bed and drawn the bed curtains. In the morning there would have been no trace of the frozen gas, which would have sublimated completely in the intervening hours, suffocating her in the process. And if any excess carbon dioxide had been in the air, it would have dissipated by the maid opening the door, the windows, and the bed curtains.
“But why?” Treadles exclaimed after he’d read the note. “Why go to such extraordinary lengths?”
“So that her parents would think exactly as they did, that their daughter perished by the will of God, and not her own hand,” said his wife sadly.
They held on to each other for a while. At the end of this silence, Alice murmured, “Do you think, my dear, that Holmes is perhaps not a real person, but an entity Lord Ingram made up so that he wouldn’t intimidate us with his vastly superior intelligence?”
“That is brilliant, my dear. Why have I not thought of it before?”
“Oh, because it’s brilliant?” She laughed. He pulled her to him for an affectionate kiss.