IT WAS FAR FROM A warm day, especially with the wind coming in off the Channel; but the sky was perfectly cloudless, the waves of the sea had nothing to reflect except the saturated azure radiance of the sky, and in consequence this was one of those rare days when the ocean really was blue. That, and the glints of gold from wave-facets catching the direct light of the sun, seemed like a favorable omen for France.

Météore nearly had not been able to get in to the harbor at Dunkirk. It wasn’t that she’d found a hostile reception. Midway across the Channel her crew had struck the Cross of St. George and run the fleur-de-lis up the mizzenmast, and the coastal batteries at Dunkirk had accepted this, or at least refrained from pulverizing them long enough for Daniel to explain himself, and send messages ashore. The difficulty had lain, rather, in finding room for one more ship in Dunkirk’s harbor. (1) A modest invasion force had gathered there in the expectation that King William would be assassinated. This was nothing like the army that had massed near Cherbourg in ’92, but it had been large enough that even now, a week after the plot had failed and the invasion had been cancelled, its remnants took up moorage-space. (2) Jean Bart, though he and his home town were as always well-fed, kept hearing reports from the interior of France that people were starving to death in large numbers; so he had sailed his fleet up north and fallen upon a hundred-ship convoy bringing Russian and Polish wheat out of the Baltic. He had defeated the Dutch naval squadron escorting it toward Amsterdam and diverted the entire convoy to Dunkirk. They were being unloaded as fast as cranes and stevedores could work, and the wheat was being taken in to famished France on endless wagon-trains that darkened the shore, and plugged the narrow ways of the town. (3) As bad as things were in France, they were worse to the north; reports had come in that during the winter just ending, one out of three Finns had died. And Scotland was not much better. Finland and Scotland were as far north as it was possible to go, and so those Finns and Scots who had been able to straggle out to the coasts and take ship had sailed south, and converged on harbors where food might be had. Many had ended up in Dunkirk.

No other ship would have been able to pass the Dunkirk breakwater, under such conditions; but when word made it up the chain of command that Météore had inexplicably returned, Captain Bart gave orders that room must be made for her; and so after some idling, Météore had been towed down a narrow lead among Baltic wheat-hulks, refugee-boats, invasion-transports, and ordinary Dunkirk fishing-and smuggling-craft to the anchorage of Bart’s privateer fleet, and given a place of honor alongside Bart’s flagship Alcyon. The first to come aboard had been a six-year-old boy armed with a wooden sword; the second, a noblewoman. She was gaunt, drawn, and black-patched compared to the last time Daniel had seen her, but he recognized her as the Duchess of Arcachon and (in England, and countries that recognized William) the Duchess of Qwghlm. And after he had talked to her for two hours, he was surprised by the awareness that she was still beautiful; just different.

And her internal fires had been banked. By the pox, he assumed at first. Then he guessed it was age—but she was not even thirty years old. On further consideration he decided it was because she had actually achieved things, and so needed not be as fierce as before. She was a Duchess twice over. She had made more fortunes than she’d lost. She had this six-year-old bastard, who seemed a fine lad, and gave every appearance of being one of those unusual children who survived to adulthood. She had a daughter of three, and a babe in arms, Louis de Lavardac, only a few weeks old—this implied she’d gone through at least as many miscarriages, stillbirths, and small-coffin funerals. Men sailed jachts across the sea and gave them to her, just to get her attention. And so perhaps her fires had been banked by choice; she’d had the sound judgment to know when to draw back, and let her investments and her children grow, and her plans come to fruition.

Daniel was invited to dine aboard Alcyon on the second day of his stay in Dunkirk—the day of the perfectly blue sky—and after he and Eliza and Jean Bart, the Marquis d’Ozoir, and a few other guests had sat round the table for some time, drinking coffee, talking, and letting the meal settle in their stomachs, Bart got up and took Jean-Jacques, or Johann as he was familiarly known, over to Météore to inspect her rigging. Daniel strolled round the decks with Eliza, drinking in the air and the sun, and watching Bart and his godson cavort about the decks, tops, and ratlines. For those two had forgotten about the ostensible purpose of the visit before they’d even come aboard the jacht, and it had turned into a sword-fighting tutorial. Bart was one of those who deemed it somehow dangerous to practice with anything other than a live, sharp, steel blade, and accordingly had armed Johann with a long knife. Bart drew a small-sword—a landlubber’s weapon, as he was dressed for dinner, not privateering. He had drawn Johann into an exercise that appeared to consist mostly of knocking Johann down (not too roughly) whenever he committed the sin of being off balance.

“In London have people heard of Father Édouard de Gex, and what befell him?” Eliza wanted to know.

“I am too retiring, too peculiar to make the social rounds and hear all the latest,” Daniel said, “and so maybe you are asking the wrong Englishman. He is a fierce Jesuit, close to the Marquise de Maintenon, and I have the vague notion that something bad happened to him—”

“You could say that,” said Eliza. “He was strolling in the gardens of Versailles late in the summer. There is a place there called the Bosquet de l’Encelade—a pool and a fountain of several jets, depressed in the center of a great encircling bower, the whole surrounded by woods, and rather remote from the château. I used to read there. As de Gex was strolling along the circuit of the bower, he became aware—or so he told the story later—that someone else was there, padding along in the same direction, but lagging far enough behind as to remain hidden from view by the curvature of the bower. And so de Gex stepped through one of the portals that gives access to the lawn within—terraced rings of turf descending toward the pool. Cutting across the lawn, he turned around abruptly to look behind him, and saw what was recognizable as a human form. But it was difficult to make out through the lattice-work of the bower. ‘Show yourself, whoever you are,’ de Gex called, and after a brief hesitation his stalker emerged from one of those portals and was revealed as an immense one-armed man carrying a long staff—which proved, on second glance, to be a harpoon. Now, the fountain lay between them, and de Gex wanted to keep it that way, whereas this other chap wanted to get closer to de Gex, so that he could launch the weapon from shorter range and without having to pitch it through jets and spray. De Gex called for help, but in this secluded part of the garden, with the roar and hiss of the fountain, he could not know whether his cry had been heard. The harpooneer took to pursuing him. De Gex was uncertain whether to keep circling the fountain—which had the advantage that it kept his adversary in view—or to exit through the bower, flee into the grove, and go for help. In any event he did not have to dither over it for long, for as it turned out someone had heard his cry and come running to see what was the matter. De Gex took his eye off the harpooneer for a moment as his would-be rescuer emerged from the bower. When he looked back he saw the harpoon inbound; for his hunter, seeing that he was losing his chance, had made a desperate fling. De Gex tried to dodge it. Meanwhile it was diverted by a surging jet from a fountain. The details are unclear; suffice it to say that the fluked head of the weapon had to be excavated, by the King’s surgeon, from deep in de Gex’s upper thigh. It passed through the muscle on the outside of the limb and spared the great vessels and nerves that run along the inside; but the bone was damaged, an infection developed, and de Gex has, ever since, lingered at Death’s door, in a sick-room at the chapter-house of the Jesuits in the town of Versailles.”

“The attacker?”

“Bolted into the forest of the King’s hunting-park and was tracked for some miles but never caught. Today I heard the news that de Gex has died. His cousin, Madame la duchesse d’Oyonnax, is looking after the arrangements—probably his body will be taken back to the family seat to be interred.”

“It is an extraordinary tale,” said Daniel. “As you have reasons for everything you do, I presume you had a reason for relating it to me?”

Eliza shrugged. “There was a feeling among some at Court that this was an assassin acting on orders from London, or some other Protestant capital. The plot to assassinate William on Turn-ham Green might have been tit-for-tat. I thought the Juncto might want to know as much.”

“I shall pass it along, then, madame. The Juncto shall consider itself in your debt.”

“I shall consider myself in yours, if you deliver the message.”

“On the contrary, it will be my honor to be of service, madame.”

“You might also be of service by escorting him home,” said Eliza, nodding over toward Johann, “assuming he survives his fencing-lesson.”

Johann had quickly tired of being knocked down by his godfather, and so the lesson had moved along to parts of the syllabus more fun and less practical: viz. hanging from ratlines with one hand whilst duelling the opponent with the other.

“I had supposed he was home,” said Daniel.

“Home is Leipzig,” said Eliza. “It is a long story—much longer than that of de Gex and the harpoon.”

“I wonder if I might engage in some tit-for-tat by telling you a bit of news from my side of the water.”

“Monsieur, I should be fascinated,” exclaimed Eliza, suddenly coming alive. “How unlike you to volunteer something!”

Daniel blushed at this, but went on: “When I was at university I was terrorized by the Earl of Upnor—Louis Anglesey. Of course he has been dead since the Battle of Aughrim. But a few days ago I phant’sied I spied his ghost standing atop a bastion of the Tower of London. Then it came into my head that he must be Upnor’s brother, Philip, Count Sheerness, who has not set foot in England for almost twenty years—he fled during the Popish Plot. England has forgotten him. But perhaps he has not forgotten England, and came back over at last to play some role in the complot to assassinate William.”

“Then England certainly will not forget him again,” Eliza said. “I wonder if he’ll be suffered to leave the Tower alive.”

“Were I a betting man, I’d bet yes. I’d bet he’ll be back on this side of the Channel before summer. Oh, he’ll be kept close for a while. Perhaps he’ll even be tried. But no proof will be found that he was involved in the plot.”

“What is your reason for telling me the story?”

“As it happens, I once was imprisoned in the same place. Some murderers were sent in to do away with me. But they were intercepted by a veteran sergeant of the King’s Own Black Torrent Guards, one Bob Shaftoe, who I believe is known to you.”

“Yes.”

“He and I made a sort of compact. He would be of aid to me in doing away with my bête noire—the late Jeffreys—if I would assist him in recovering a certain young woman—”

“I know the story.”

“Very well. Then you know she is a slave, once owned by the Earl of Upnor, but distributed to Count Sheerness as a part of Upnor’s estate when Upnor was killed at Aughrim. I presume she has been on this side of the water, serving in Sheerness’s household.”

“Indeed. What is it you would have me do, Dr. Waterhouse?”

“The Black Torrent Guards have been in the Spanish Netherlands for some years, fighting the war, whensoever the Juncto could scrape together money for balls and powder. I thought perhaps you might know of some way of getting word to Sergeant Shaftoe that the owner of Abigail is in a tight spot just now, and unable to defend his properties on the Continent. Between that, and the lull in the fighting, there might be opportunity—”

“Other such opportunities have come his way in the past, but he has not been quick to take advantage of them,” said Eliza, “because he has been looking after his nephews, and could not see a way to fulfill so many obligations at once. But his nephews must have reached the age of manhood by now. Perhaps he is ready.”

“That must have vexed their uncle to no end,” Daniel mused.

“Yes. But it must have made his life a good bit simpler, too,” said Eliza. “So, consider the message delivered and your obligation discharged, Dr. Waterhouse.”

“Thank you, your grace.”

“You are most welcome.”

“—”

“Is there anything else?”

“Nothing that I would dream of mentioning to any ordinary Duchess—or woman, for that matter. But as you have an interest in money, here is a curiosity for you.”

Daniel reached into both hip-pockets at once. From each he drew a sheaf of printed bills, and held them out, rather like the two pans of a balance, so that Eliza could inspect them. The offerings on left and right were similar, but different. Clearly there had been a lot of work for engravers in London lately, for these documents had been pressed out by copper-plates of awesome complication: miles of line folded up into inches of space, like the windings of testicles. One depicted a goddess gripping a trident and sitting upon a great mound of coins. “Even by Barock standards, the most vulgar thing I’ve seen,” Eliza pronounced it. BANK OF ENGLAND, it said; and below that was printed a florid and verbose assertion that it—which is to say, this piece of paper—was money. The bills on Daniel’s opposite hand said LAND BANK and supported like claims—if anything, even more pompous.

“Whig,” said Daniel, shaking the BANK OF ENGLAND bills, “and Tory,” shaking the LAND BANK bills.

“You even have different money!?”

“The Bank of England was, as you must know, set up two years ago by the Juncto after it won the election. It is backed—these bills are backed—by the ability of the government to raise money from taxes, lotteries, annuities, and whatever other schemes the big brains of the Juncto can think up. Not to be outdone, the Tories set up their own Bank, backed by—”

“The land of England itself? How Tory-like.”

“They are nothing if not consistent.”

“Curious. Are these worth anything?”

“As always, you go to the heart of the matter. In the absence of any other money, these do circulate in London. The Marquis of Ravenscar, who gave these to me, asked that I present them to you, and try to—to—”

“To exchange them for specie?” Eliza laughed. “Cheeky fellow! So it is an experiment! A little foray into Natural Philosophy. He wishes you to gather some data on your Continental tour—to see if anyone outside of England heeds the promises stamped on these bills.”

“Something like that. I am relieved that you take it in such good humor.”

“Let me ask you this, Doctor: what is the exchange rate between Whig and Tory money?”

“Ah. At the moment, one of these—” he held up the Land Bank notes “—buys rather a lot of these.” He indicated the Bank of England notes. “For many are of the view that the Bank of England has failed already, and the Land Bank is ascendant.”

“Which amounts to saying that the Juncto will be cast down in the next election, and Harley will lead the Tories to victory.”

“I dare not disagree—as much as I’d like it otherwise.”

“Then I shall buy a few of these, in exchange for a Bill of Exchange, denominated in thalers, and payable at the House of the Golden Mercury in Leipzig,” said Eliza, indicating the Land Bank notes, “but I shall exchange them immediately for a lot of these.” She licked a finger and began to count off Bank of England notes.

“You place your trust in the Whigs? Roger shall be overjoyed.”

“I place my trust in Newton,” Eliza said.

“You refer to his new position at the Mint.”

“I had more in mind the calculus.”

“How so?”

“This is really a matter of derivatives, is it not?”

“Financial derivatives?”

“No, mathematical ones! For any quantity—say, position—there is a derivative, representing its rate of change. As I see it, England’s stock of land represents a fixed quantity of wealth. But commerce I see as a derivative—it is the slope, the speed, the rate of change of the nation’s wealth. When commerce stagnates, this rate of change is small, and money founded upon it is worthless. Hence the lopsided exchange rate you told me of. But when commerce thrives, all goes into rapid movement, the derivative jumps up, and money founded on it becomes of much greater value. Once Newton goes to work at the Mint, the supply of coin in England can only improve. Commerce, which has been frozen for lack of money, will surge, at least briefly. The exchange rate between these two currencies will swing the opposite way, long enough at least for me to take a profit.”

“It is a way of looking at the thing I had not considered before,” said Daniel, “and it sounds right to me. But if you ever have an opportunity to expound your theory to Isaac, I hope you’ll use the word fluxion in place of derivative.”

“What’s a fluxion?”

“That,” said Daniel, “is the problem in a nutshell.”