“That is the second time today I have heard ‘Black-guard’ spoken in those portentous tones. I thought a Black-guard was a boy who polished boots.”

“Some of those boys have got rather big, and found employment even lower, and even blacker,” Isaac remarked.

“Then I’ll have nothing to do with any Black-guard.”

“If you have heard some other man speaking the word to-day, ’twould seem that you already do have something to do with them,” said Isaac, amused, “which would hardly surprise me considering the company you have been keeping.”

Daniel was silent. But only because he could not divulge to Isaac that his only motive in speaking to the sort of man who spoke of the Black-guard-men such as Peter Hoxton-was to track down whatever remnants Hooke had left behind.

Isaac read his silence as submission. Given more time, Daniel might have disabused Isaac of any such ideas, and extricated himself. But a servant was knocking at the door. A minute earlier Daniel had heard someone calling briefly at the front door of the house, presumably to deliver a message, and now it had penetrated to the study, and interrupted their discourse at the worst possible moment for Daniel. He wondered whether the servant had been lurking outside the door, waiting to knock at some subtle signal from Isaac: I have sprung the trap, now interrupt us lest he wriggle free!

“Enter!” Isaac commanded, and in came the servant who’d admitted Daniel earlier, holding a rectangle of good paper with a few lines scrawled over it in a lazy, important hand. As Isaac decyphered the penmanship, and considered the import, and discussed it in a hushed, elliptical manner with his servant, Daniel had his first opportunity to review all that had passed since he had breezed into this room with a riddle concerning guineas.

What had he expected? He had expected that, at best, Isaac would be cool and distant. At worst, he’d know that Daniel was striving to preserve some memory of Hooke, and corresponding with and running errands for Leibniz, and would tear Daniel’s beating heart out of his chest then and there, like an Aztec priest. Those had seemed the most likely outcomes. If some oracle had let him know in advance that he was to have a long, cordial, even friendly conversation with Isaac, he’d have accounted it a triumph. And maybe it was-but it was Isaac’s triumph and not Daniel’s. Whether or not Isaac knew of Daniel’s concealed loyalty to Hooke and Leibniz, he had clearly got it into his mind that Daniel needed to be kept close, and kept busy.

“We’ve not even had time to broach the subject of Baron von Leibniz’s pretensions concerning the calculus,” Isaac announced in a chummy voice that was very odd coming from him, “and here it is time for me to be on my way.”

“I consider myself fortunate indeed to have taken up as much of your time as I have done,” Daniel said, trying not to sound ironic about it.

“The good fortune is all mine, and I assure you that the meeting I go to now shall never be half so enjoyable as this!” Isaac returned. “If the Mint were strictly a temple of Natural Philosophy-as it ought to be-supervising it would be pure pleasure. As it is, I waste many hours in meetings of a political nature.” He was getting to his feet.

“Is it Whigs or Tories today, then?” Daniel asked, rising. From here on out it would be all banter: pleasant noises that might as well have been spoken in Iroquois.

“Germans,” Isaac returned, offering him priority out the door. Catherine Barton, or someone, must have taught him manners.

“Really! They’ll be running the country soon enough, why are they pestering you now?”

They paused in a hall so that Isaac could shrug off his scarlet robe and have a vest and coat thrown across his shoulders by a valet. “They don’t pester me, but other men, of higher station-ramifications ensue,” Isaac said. “I would offer to convey you somewhere, but my conveyance only has room for one. May I have a hackney summoned for you?”

“I’ll walk, thank you,” Daniel said. Isaac followed him into the vestibule, which was crowded. Two large men were in here, smelling of the street. Between them stood a vertical black box, open on one side to reveal a crimson leather seat. Isaac sidled into it, smoothing the skirts of his coat under him. A servant stood at the ready to slam the door to.

“I shall hear from you concerning the proposal that I made,” Isaac predicted. “And do let’s not forget to have a conversation, some day soon, about the calculus.”

“Not a day passes without my thinking of it,” Daniel answered. With that the door was latched shut. Isaac had vanished inside the black box. His voice came out of it clearly, “God save the Queen, Daniel,” reminding Daniel that the only thing between them was a sheer black screen through which Isaac could see and hear everything, though he was quite invisible to anyone outside.

“God save the Queen,” Daniel returned, and then he followed the sedan chair out the door and onto St. Martin’s. Isaac was carried rapidly southwards, toward St. James’s and Westminster and all things great and important. Daniel, not wanting the awkwardness of walking along abreast of Isaac’s chair, went the other way.

Passing immediately through a gate at the head of the lane, he came out into an open plaza, squarish, about a bow-shot on a side. This was called Leicester Fields, and on three sides-including the one where Daniel had entered-it was now hemmed in by the sort of new town-houses that had started going up all round here after the Fire. But on the north edge-which Daniel was facing directly across a few hundred feet of open turf-it was walled off by one of the few remaining old-fashioned Tudor compounds: a congeries of red brick and half-timbered buildings called Leicester House. It had formerly been one of the few houses around London deemed suitable for royalty to dwell in, and had been used by diverse Tudor and Stuart princes as a palace. Elizabeth Stuart had dwelt there before she’d gone off to Europe to become the Winter Queen and to spawn Sophie and many others. Changes in the royal line had weakened the sentimental ties to this house, and the re-building of London in a new style had quite over-shadowed it and made it seem a mere English farm-house.

As Daniel came into Leicester Fields, he gazed in that direction curiously, trying to get his bearings, like a mariner looking for the old familiar stars. He saw a lot of horses and vehicles in front of the place, and felt a pang, supposing that the wreckers had arrived to tear it down. But as he strolled across the Fields, creating localized panics among sheep and chickens, he perceived that these were not rubbish-wagons but baggage-carts, and rather well-maintained ones at that. Among them was a carriage, a coach-and-four drawn by a matched set of black horses. A woman was alighting from that carriage, walking away from Daniel toward the house, and servants were drawn up in two lines to greet her. Daniel could not see anything of the woman, other than that she was petite, and trim. Her head was shrouded in a voluminous silk scarf covering a big hat or wig. And he was too far away, and his eyes were too far gone, to resolve lips, eyes, and noses on the faces of those servants. But something in their posture, and in the way they turned their faces and bodies toward the woman as she progressed across the court, told Daniel that they were smiling. They loved her.

At the apex of this formation, where the two lines of servants came together in front of the house’s main entrance, stood a man who was not a servant: he was dressed in the clothes of a gentleman. But there was something odd about him, which Daniel could not make sense of until he went into movement, extending a leg to make a low bow, and accepting the woman’s hand to kiss it. The man’s skin was entirely black. The woman took his arm and the black man escorted her into Leicester House; the lines of servants broke up and everyone made him- or herself busy unloading the baggage carts, amp;c.