The sculpture was heavy-laden with clews and portents: with her free hand Minerva was already reaching for a rag, and Vulcan was ominously close to making contact with her creamy thigh. Smaller sculpture groups decorated the ends of the fountain-pool; at the end nearer to Daniel’s building, a babe on the lap of a fertility sort of goddess (lots of cornucopiae) being fed grapes from a bunch. Opposite, near Vanbrugh’s building, a crowned King seated on a pile of bullion. As they skirted the pool, Daniel felt a perverse urge to swivel his head and find out just how the sculptor had handled certain particulars. He was especially keen to know from where the water was spurting. At the same time, he couldn’t bear to see it. Catherine was ignoring the fountain altogether; she did not want to talk about it, had turned her face away, her posture rhyming with Minerva’s. Daniel contented himself with pursuing her across the court-yard, albeit with even less success than Vulcan.

What with so many distractions, they were inside the new house before Daniel had really had the time to examine its interior. Probably just as well; he’d gotten a vague impression of lots and lots of statues, prancing along rooftops and balustrades.

“Rokoko, it is called,” Catherine explained, leading him into what must have been the grand ballroom. “ ’Tis all the rage.”

Daniel could only recollect Drake’s house, with its bare walls and floors, and one or two plain boxy pieces of furniture to a room. “It makes me feel old,” he said, baldly.

Catherine favored him with a brilliant smile. “Some say, ’tis the result of a surplus of decorators, combined with a deficit of houses.”

And a want of taste, Daniel wished he could say. “As you are the mistress of the household, mademoiselle, I shall make no comment on what some say.” She rewarded him with dimples. Without meaning to, he had made a sly comment on her Arrangement with Roger.

Daniel found these moments slightly unnerving. For the most part she did not look like Isaac-not even the young, frail, girlish Isaac Daniel had met at Trinity half a century ago. He would never have guessed she had a drop of Newton-blood in her veins if he hadn’t known as much already. But during the moments when she forgot to hide her cleverness, a family resemblance flashed forth, and he saw Isaac’s face for an instant, as if the author of Principia Mathematica were stalking him through a darkened room when lightning struck outside.

“Here is a curious invention you may find worthy of your attention, Doctor. This way, please!”

The volcano stood at one end of the ballroom. It was a great improvement on the volcanoes made by Nature, which were so rude, irregular, and unadorned. This one was perfectly conical, with forty-five-degree-angle slopes converging on a polished brass nozzle or teat at the summit. A semi-ruined Classical temple, complete with half-collapsed golden dome, had been erected there, enclosing the vent, which could be viewed between Doric columns of red marble. The mountain itself was black marble, veined with red, and adorned with the usual tiresome menagerie of nymphs, satyrs, centaurs, amp;c., all sculpted in gold. It probably stood no more than four feet from base to summit, but was made to seem much larger by the base that supported it: a hollow plinth rising from the floor to waist level, supported all round with caryatids in the shape of Typhon and other gross earthy monsters.

“If you come round back with me, Doctor, I shall a-maze you with the most marvelous Screw.”

“I beg your pardon?”

She had opened a hatch concealed in the back, and was beckoning. He came round, squatted carefully, and peered inside. Now he could see a fat cylinder that began in a copper basin on the floor, and ran up at an angle to the summit of the volcano.

“Roger wanted so badly to have a volcano that would spew rivers of molten silver. It would have been spectacular! But Mr. MacDougall was afraid it would set fire to the guests.”

“Which would have been spectacular too, in a different way,” Daniel mused.

“Mr. MacDougall persuaded Roger to settle for oil of phosphorus. It is prepared elsewhere, and brought here in casks, and poured into the tub. The Screw of Archimedes conducts it upwards, it gushes from the summit, and runs down the slopes as the centaurs and whatnot flee in terror.”

“They-flee?”

“Oh, yes, for it is meant to represent glowing streams of liquid fire.”

“That I understand. But how do they flee-?”

“They are clock-work creatures.”

“Also the work of Mr. MacDougall?”

“Indeed.”

“I remember hiring a silversmith named Millhouse but not an ingenieur named MacDougall.”

“Mr. Millhouse hired Mr. MacDougall to do the clever bits. When Mr. Millhouse died of smallpox-”

“Mr. MacDougall took over,” Daniel guessed, “and could not stop adding one clever bit after another.”

“Until Roger cut him off-somewhat emphatically, I’m afraid,” said Catherine, and winced in a manner that made Daniel want to stroke her hair.

“Is he still alive?”

“Oh, yes, he works in theatres, making apparitions, explosions, and storms.”

“Of course he does.”

“He staged the naval battle that burned down the Curtain.”

“I believe you. How frequently does the volcano erupt?”

“Once or twice a year, for important parties.”

“And Mr. MacDougall is called back from exile on those occasions?”

“Roger has him on retainer.”

“Where does he get his phosphorus?”

“He has it delivered,” she said, as if this were an answer.

“Where may Mr. MacDougall be found, I wonder?”

“The Theater Royal, in Covent Garden, is getting ready to stage a new production entitled The Sack of Persepolis,” Catherine said, tentatively.

“Say no more, Miss Barton.”

“I’VE A SORT OF RIDDLE for you, to do with guineas,” was how Daniel ended the twenty-year silence between himself and Sir Isaac Newton.

He had been fretting, ever since Enoch Root had turned up in his doorway in Massachusetts, over how to begin this conversation: what ponderous greeting would best suit the gravity of the occasion, how much time to spend reminiscing about student days in Cambridge, and whether to say anything about their last encounter, which had gone as badly as any social encounter, short of homicide, could go. Like a play-wright penning and burning draughts of a troublesome scene, he had scripted this reunion in his head an hundred times, and each time the script had careered off into a bloody debacle like the last act of Hamlet. As it seemed perfectly hopeless, and as he’d been assured by Saturn that he had only hours or days to live in any case, he reckoned, why waste time on formalities?

When the door was opened, and he first looked Isaac in the face from across the room, he did not see any trace of fury or (what would have been more dangerous) fear. Isaac looked resigned. He was feigning patience. He looked like a Duke receiving a long-lost idiot half-brother. And on the spur of the moment, Daniel said this thing about guineas as he was stepping over the threshold. The servant who’d opened the door for him gave him the same sort of look he might bestow on a gibbeted corpse suspended above a crossroads on a warm day, and closed the door behind him.

Daniel and Isaac were alone together in the study. Or Daniel assumed it was called a study. He could not imagine Isaac having a bedchamber or a dining-room. Any room he was in, was a study by default. The walls were paneled in dark wood, surprisingly uneven, almost rustic, compared to Roger’s house. The door was made of the same stuff, so that it vanished when it was closed, making it seem as if Daniel and Isaac were a pair of old desiccated specimens closed up in a shipping crate. The room had windows looking out onto the street. Their massive, elaborate wooden shutters were open to admit some of the light off Leicester Fields, but much of this was blocked by half-drawn scarlet curtains. Isaac was seated behind a great table, the sort of table Drake would’ve owned, and he was dressed in a long scarlet dressing-gown over a good linen shirt. His face had not changed all that much, though it had got heavier, and he still had the long white hair. But his hairline had jumped back, making it seem as if his brain were trying to force its way up out the top of his head. His skin had been white when Daniel had walked in, but by the time he had made it to the end of the room to proffer his hand, Isaac had gone red in the face, as if stealing the color from his robe.