DANIEL WATERHOUSE REMOVED a handkerchief from his breast pocket, draped it over his hand, and used it to grip the handle of the assassin’s dagger. The weapon had been borne into the room-a servants’ pantry near Princess Caroline’s apartment-on a silver tray, like an hors d’ouevre. Daniel held it several inches above a candle, so that the blade split the current of warm air rising from the flame. Then he leaned forward and got his beak into a position some distance above that. He gave the air the tiniest sniff, then recoiled and turned away from it. The dagger he set back on the tray, and the handkerchief he wadded up and threw into a cold fireplace in the corner of the pantry.

Johann could smell it now, too: an acrid, smoky reek that reminded him of something.

“Nicotine,” said Daniel.

“Never heard of it.”

“That may be, but you have some in you right now, if you have smoked a pipe in the last few hours.”

“That’s what the smell reminds me of, a bit-an old pipe-bowl that has never been cleaned out.”

“It is an extract of the tobacco plant. When I was your age, it was in vogue, among certain Fellows of the Royal Society, to prepare this poison and inflict it on small animals. It is soluble in oil. It is bitter-”

“You’ve tasted it?!”

“No, but persons who have, invariably remark on its bitterness before they stop breathing.”

“How does it kill?”

“I have just told you-the victim stops breathing. But not before becoming twitchy and spasmodic for a brief time.”

“That was true of the dog, when I saw it. Then I lit out in pursuit of the other assassin. He had been pursued to the edge of the canal, and jumped in rather than perish at sword’s edge. He was sloshing about-for the water was but chest-deep-looking for some apt place to scale the opposite wall of the channel. Then he stopped moving, and sank below the surface. When we pulled him out he was dead.”

“Did water drain from his lungs?”

“Now that you mention it, no.”

“He did not drown then,” Daniel said. “If you examine the corpse carefully you shall find some place where he nicked himself with his dagger, or let it brush against his skin.” Daniel planted a hand to either side of the silver platter and gazed at the weapon. “This is an expert preparation, solved in some fine light oil, such as whale-oil. Smeared on the skin it would convey the nicotine into the capillaries and thence to the lungs in a few minutes’ time.” He looked up at Johann. “When you smoke your pipe, you feel an initial rush of stimulation, followed by a calmness, a steadying of the nerves. This is but a trace, a shadow, of nicotine poisoning. If you were cut with this dagger, that relaxation of the nerves would advance to the point where you would simply forget to breathe, and drown in air…every time you smoke tobacco, you are prefiguring your own death.”

“Horrid…it makes me want to smoke something just to calm down.”

“Mr. Hooke experimented with an herb called bhang that would cure what ails you-alas, it is harder to get.”

“I shall make inquiries. It is strange. During the events, I had a clarity of mind, a sharpness of perceptions, I’d never known before. Now, sitting here, I am terrified.”

“As I should be, if I had just received such a tongue-lashing from the Duchess of Arcachon-Qwghlm.”

“You could hear it this far away?”

“I do believe that the King of France sat up in his bed at Versailles wondering what new war had broken out in Germany.”

“It’s true, I have never seen her so angry. She did tell me never to duel. And I did promise. But this-”

“You chose the moment well,” Daniel assured him. “Physical violence is a means that I have never employed for any purpose. The risks are enormous, and a man of my mentality, who sees dangers where they are and are not, can always find a reason to take some other course. You are young and-”

“Stupid?”

“No, but less perceptive of risk. When, God willing, you have reached the age of forty, you’ll sit up in bed in the middle of the night, covered in sweat, with the memory of this night fresh in your mind, and say, ‘My God, I cannot believe I once fought a duel!’ Or so I hope.”

“Why do you hope for me to sleep poorly?”

“Because though I have not done violence I have seen rather a lot of it. Not all of the men who employ it are stupid, or evil. Only most of them. The rest use it reluctantly, as a way, when all else has failed, of seizing the main chance. Thus you tonight. Your mother will understand this and get her equilibrium back. But like a man who imbibes tobacco-smoke, you have died a little death tonight. I do not recommend that you become addicted to it.”

“It is very good advice. I thank you for it. As I thank you, again, for giving us information that saved Caroline’s life. You may expect that she will reward you-”

“I would glady forgo all thanks and rewards if I could simply take a nap.”

“You can nap in the carriage, Dr. Waterhouse,” said a woman’s voice. Hoarse, as if she’d been screaming a lot recently.

Daniel and Johann both looked over to see Eliza in the pantry’s doorway. She looked a good deal calmer.

“My lady,” Daniel said, and sighed, “from any other woman I should interpret this as a jest or non sequitur, but from you I fear-”

“It is well known that you stayed behind in Hanover, being too ill for arduous travel-”

“Thank you for reminding me, my lady, my infirmity had quite slipped my mind.”

“It is expected that you will take the slow way back, attended by a nurse. I give you your nurse.” Eliza came all the way into the room now. She was followed by a young woman dressed in a severe habit, her head swaddled in a length of white linen that had been wrapped around so as to conceal all of her hair, and a good bit of her face-hardly a la mode, but not particularly unusual in a time and place when nearly everyone sooner or later got smallpox, and some emerged in good health but almost impossible to look at. “This is Gertrude von Klotze, a petty noblewoman of Braunschweig, who after suffering and surviving a grave illness, has dedicated the remainder of her life to succouring others in need.”

“A noble woman indeed. It is my very great pleasure to meet you, mademoiselle,” said Daniel, adroitly looking past the fact that this woman was, in fact, Princess Caroline.

“Fraulein von Klotze shall accompany you all the way to London.”

“And how shall sweet Gertrude get back?” Johann demanded-having taken a few moments to recover from the abrupt transfiguration of his lover into a masked nurse. He made a step toward Caroline, but she sent him back with a dart of the eyes. “Surely her family will miss her!”

“Perhaps she won’t have to come back, as her family may be moving to London soon anyway,” Eliza said. “Gertrude shall lodge at Leicester House until we make rendezvous with her later.”

“I did not know that I was-we were-going to London!” Johann answered.

“We are,” Eliza said calmly, “but not before a detour to the chateau at Schlo? Ubersetzenseehafenstadtbergwald.”

“Eeyuh, that place? Are you joking? What’ll we do there, hunt bats?”

“Some minutes ago, you may have heard a woman screaming in this wing of the palace.”

“Indeed, my ears are still ringing.”

“That was Princess Caroline.”

“Are you certain? For during the time this screaming reached my ears I observed movements of your lips, Mother, curiously synchronized-”

“Your wit is tedious. ’Twas the Princess. Her grief over the death of Sophie is even deeper than was realized. Her braveness earlier today a mere affectation, masking a profound derangement of the nerves. Not long ago, she simply dissolved. She has been given tincture of opium and is under strict seclusion in her bedchamber. Before the sun is up, she shall be taken out in a sedan chair and loaded into my carriage. You, son, and I shall convey her to the Schlo? I have mentioned-one of the most remote and desolate out-croppings in Christendom. There, her royal highness shall spend several weeks in seclusion, tended only by a few trusted servants, turning away all visitors.”