Daniel ascended the stairs, moving purposefully, as if he actually knew his way around the place. In fact, all he had to go on was vague memories of what he’d spied through the telescope twenty years ago. If they served, the room where Upnor and Newton had met was dark-paneled, with many books. Daniel had been having odd dreams about that room for two decades. Now he was finally about to enter it. But he was dead on his feet, so exhausted that everything was little different from a dream anyway.

At least a gross of candles were burning in the stairs and the upstairs hall: little point in conserving them now. Cobwebby candelabras had been dragged out of storage, and burdened with mismatched candles, and beeswax tapers had been thrust into frozen wax-splats on expensive polished banisters. A painting of Hermes Trismegistus had been pulled down from its hook and used to prop open the door of a little chamber, a sort of butler’s pantry at the top of the stairs, which was mostly dark; but enough light spilled in from the hall that Daniel could see a gaunt man with a prominent nose, and large dark eyes that gave him a sad preoccupied look. He was conversing with someone farther back in the room, whom Daniel could not see. He had crossed his arms, hugging an old book to himself with an index finger thrust into it to save his place. The big eyes turned Daniel’s way and regarded him without surprise.

“Good morning, Dr. Waterhouse.”

“Good morning, Mr. Locke. And welcome back from Dutch exile.”

“What news?”

“The King is run to ground at Sheerness. And what of you, Mr. Locke, shouldn’t you be writing us a new Constitution or something?”

“I await the pleasure of the Prince of Orange,” said John Locke patiently. “In the meantime, this house is no worse a place to wait than any other.”

“It is certainly better than where I have been living.”

“We are all in your debt, Dr. Waterhouse.”

Daniel turned round and walked five paces down the hall, moving now towards the front of the house, and paused before the large door at the end.

He could hear Isaac Newton saying, “What do we know, truly, of this Viceroy? Supposing he does succeed in conveying it to Spain-will he understand its true value?”

Daniel was tempted to stand there for a while listening, but he knew that Locke’s eyes were on his back and so he opened the door.

Opposite were the three large windows that looked over Charing Cross, covered with scarlet curtains as big as mainsails, lit up by many tapers in sconces and candelabras curiously wrought, like vine-strangled tree-branches turned to solid silver. Daniel had a dizzy sensation of falling into a sea of red light, but his eyes adjusted, and with a slow blink his balance recovered.

In the center of the room was a table with a top of black marble shot through with red veins. Two men were seated there, looking up at him: on Daniel’s left, the Earl of Upnor, and on his right, Isaac Newton. Posed nonchalantly in the corner of the room, pretending to read a book, was Nicolas Fatio de Duilliers.

Daniel immediately, for some reason, saw this through the suspicious eyes of a John Churchill. Here sat a Catholic nobleman who was more at home in Versailles than in London; an Englishman of Puritan upbringing and habits, lately fallen into heresy, the smartest man in the world; and a Swiss Protestant famous for having saved William of Orange from a French plot. Just now they’d been interrupted by a Nonconformist traitor. These differences, which elsewhere sparked duels and wars, counted for naught here; their Brotherhood was somehow above such petty squabbles as the Protestant Reformation and the coming war with France. No wonder Churchill found them insidious.

Isaac was a fortnight shy of his forty-sixth birthday. Since his hair had gone white, his appearance had changed very little; he never stopped working to eat or drink and so he was as slender as he had always been, and the only symptom of age was a deepening translucency of his skin, which brought into view tangles of azure veins strewn around his eyes. Like many College dwellers he found it a great convenience to hide his clothing-which was always in a parlous state, being not only worn and shabby but stained and burnt with diverse spirits-underneath an academic robe; but his robe was scarlet, which made him stand out vividly at the College, and here in London all the more so. He did not wear it in the street, but he was wearing it now. He had not affected a wig, so his white hair fell loose over his shoulders. Someone had been brushing that hair. Probably not Isaac. Daniel guessed Fatio.

For the Earl of Upnor it had been a challenging couple of decades. He’d been banished once or twice for slaying men in duels, which he did as casually as a stevedore picked his nose. He had gambled away the family’s great house in London and been chased off to the Continent for a few years during the most operatic excesses of the so-called Popish Plot. He had, accordingly, muted his dress somewhat. To go with his tall black wig and his thin black moustache he was wearing an outfit that was, fundamentally, black: the de rigueur three-piece suit of waistcoat, coat, and breeches, all in the same fabric-probably a very fine wool. But the whole outfit was crusted over with embroidery done in silver thread, and thin strips of parchment or something had been involved with the needle-work to lift it off the black wool underneath and give it a three-dimensional quality. The effect was as if an extremely fine network of argent vines had grown round his body and now surrounded him and moved with him. He was wearing riding-boots with silver spurs, and was armed with a Spanish rapier whose guard was a tornadic swirl of gracefully curved steel rods with bulbous ends, like a storm of comets spiraling outwards from the grip.

Fatio’s attire was relatively demure: a many-buttoned sort of cassock, a middling brown wig, a linen shirt, a lace cravat.

They were only a little surprised to see him, and no more than normally indignant that he’d burst in without knocking. Upnor showed no sign of wanting to run him through with that rapier. Newton did not seem to think that Daniel’s appearing here, now, was any more bizarre than any of the other perceptions that presented themselves to Isaac in a normal day (which was probably true), and Fatio, as always, just observed everything.

“Frightfully sorry to burst in,” Daniel said, “but I thought you’d like to know that the King’s turned up in Sheerness-not above ten miles from Castle Upnor.”

The Earl of Upnor now made a visible effort to prevent some strong emotion from assuming control of his face. Daniel couldn’t be certain, but he thought it was a sort of incredulous sneer. While Upnor was thus busy, Daniel pressed his advantage: “The Gentleman of the Bedchamber is in the Presence as we speak, and I suppose that other elements of Court will travel down-river tomorrow, but for now he has nothing-food, drink, a bed are being improvised. As I rode past Castle Upnor yesterday evening, it occurred to me that you might have the means, there, to supply some of His Majesty’s wants-”

“Oh yes,” Upnor said, “I have all.”

“Shall I make arrangements for a messenger to be sent out then?”

“I can do it myself,” said the Earl.

“Of course I am aware, my lord, that you have the power to dispatch messages. But out of a desire to make myself useful I-”

“No. I mean, I can deliver the orders myself, for I am on my way to Upnor at daybreak.”

“I beg your pardon, my lord.”

“Is there anything else, Mr. Waterhouse?”

“Not unless I may be of assistance in this house.”

Upnor looked at Newton. Newton-who’d been gazing at Daniel-seemed to detect this in the corner of his eye, and spoke: “In this house, Daniel, a vast repository of alchemical lore has accumulated. Nearly all of it is garbled nonsense. Some of it is true wisdom-secrets that ought rightly to be kept secret from them in whose hands they would be dangerous. Our task is to sort out one from the other, and burn what is useless, and see to it that what is good and true is distributed to the libraries and laboratories of the adept. It is difficult for me to see how you could be of any use in this, since you believe that all of it is nonsense, and have a well-established history of incendiary behavior in the presence of such writings.”