THEY DREW ALONGSIDE A WHARF at Gravesend. It was near where the tilt-boat ran up the river to London, and so a sizable and curious crowd was there watching them, and calling out questions. Perhaps Isaac thought his outburst about “the German” really was an intelligible end to the conversation, or perhaps he did not care to stand in the open on the poop and be peered at.

Daniel sensed he was being peered at from another quarter. A certain gentleman had been haunting the corner of Daniel’s eye for above a quarter of an hour. From his dress, he was an officer of the Queen’s Own Black Torrent Guards.

“Colonel Barnes,” the man said, in response to what must have been a lapse in Daniel’s mean, flinty outlook.

“I am Dr. Daniel Waterhouse,” Daniel returned, “and I have heard criminals introduce themselves to me with greater formality and courtesy than what you have just shown.”

“I know,” said Colonel Barnes, “one of them came up to me and did just that, a few hours ago, on Tower Wharf.”

“Colonel Barnes, ’twould seem you have duties ashore, I’ll not delay you-”

Barnes glanced out over the sloop’s upperdeck, which had now been joined to the wharf by gangplanks in two places. Dragoons were streaming across, driven by cursing sergeants on the deck and exhorted by lieutenants on the wharf; as they came ashore they clustered by platoon.

“On the contrary, Dr. Waterhouse, I’m to stay ’board ship. Suits me better.” He made a loud rapping noise on the deck, and Daniel looked down to discover that one of the colonel’s legs was a rod of carven ebony with a steel tip.

“You are a Black Torrent man to the bone,” Daniel remarked. Every regiment had its own type of wood, used to make swagger sticks and the like, and ebony was the trade-mark of the Black Torrent Guards.

“Indeed, been with them since the Revolution.”

“Surely you need to supervise the disembarkation-”

“Dr. Waterhouse, you do not understand Delegation of Authority,” Barnes returned. “Here’s how it works: I tell my subordinates to get all but two platoons off the boat, and they do it.”

“Who has delegated you to harry me round the poop deck?”

“Why, the aforementioned very polite criminal.”

“A colonel commands a regiment, is it not so?”

“That is correct.”

“Do you mean to tell me that a colonel, in turn, is commanded by a Black-guard?”

“That is the custom in most armies,” Barnes returned dead-pan. “True, ’twas sometime different under my lord Marlborough, but since he was stripped of command, why, it has been Black-guards all the way to the top.”

Daniel had a natural impulse here to laugh; but some other part of him was recommending that he proceed cautiously with this Barnes. What the colonel had just said was witty, but it was also reckless.

Most of the Guards were off the ship now, leaving only two platoons of some fourteen men each, each under its own sergeant. One of them had congregated at the forward end of the deck, the other aft, directly below where Colonel Barnes and Daniel were standing. This left a large clear space amidships, claimed by Sergeant Bob Shaftoe. He was facing toward the wharf, so Daniel was viewing him in profile; but now he adjusted his posture slightly toward them and glanced, for a quarter of a second, in Barnes’s direction.

“Your sloop, Cap’n,” Barnes sang out.

The skipper retaliated with a series of histrionic commands that caused the gangplanks to be drawn back onto the wharf, and the sloop’s lines to be cast off.

“You and Sergeant Bob make war together,” Daniel said. “It is what you do.”

“If that’s true, our life’s work has been a failure!” Barnes answered, mock-offended. “I should prefer to say, we make peace, and have achieved success.”

“Say it however you like. Either way, you’ve spent a quarter-century marching around with him, and have heard every joke and anecdote he knows how to tell, a thousand times over.”

“ ’Tis a common outcome in our line of work,” Barnes allowed.

“Now you phant’sy you know everything about me, because ten or twenty years ago, in a tent along the Rhine or a bothy in Ireland, Sergeant Bob told you a tale about me. You suppose you may approach me in a companionable way, and divulge things to me, and thereby make me your bound accomplice, as when two boys cut their thumbs on purpose and bleed on each other and then say that they are brothers. Please do not be offended if I recoil from your tender. There is a reason why old men are aloof, and it has nothing to do with being pompous.”

“You should renew your acquaintance with Marlborough,” Barnes said, putting on a little show of being impressed. “The two of you would get along famously.”

“An unfortunate choice of adverb, that.”

Barnes was silent for a while now. The two horse-barges were coming up to the wharf at Gravesend to discharge the loads. The Queen’s Own Black Torrent Guard were dragoons, meaning that they fought on foot, using the tactics and the arms of infantry. But they maneuvered round the field of battle on horseback. To put it crudely, they were shock troops. Clearly the companies that had disembarked had orders to mount, get on the turnpike that paralleled the river, and ride east, pacing the sloop.

“Everyone is scared to death just now,” Barnes said. He sidled up to Daniel along the rail and offered him half a small loaf of bread, which Daniel practically lunged at. “Why, to listen to certain Whigs, a Jacobite invasion is just over the horizon, driven on a Popish wind. And yet Sir Isaac fears the arrival of the German! ’Tis an impossibility for both the Hanovers and the Jacobites to occupy the same space. Yet the Whigs’ fears, and Sir Isaac’s, are equally real.”

When he alluded to the impossibility of two objects occupying the same space, Barnes was resorting to a verbal tic that had its origins in Descartes. He had, in other words, been to Oxford or Cambridge. He ought to be a vicar, or even a Dean, in some church. What was he doing here?

“When Sir Isaac refers, with such trepidation, to the German, he does not mean George Louis.”

Barnes looked startled, then fascinated. “Leibniz-?”

“Yes.” And this time Daniel could not prevent himself smiling a bit.

“So it’s not that Sir Isaac is a Jacobite…”

“Far from it! He fears the arrival of the Hanovers, only in that Leibniz is the advisor to Sophie, and to Princess Caroline.” Daniel wasn’t entirely certain he ought to be telling Barnes so much, but it was better for Barnes to understand the truth than to harbor the suspicion that Isaac was a covert supporter of the Changeling.

“You skipped a generation,” Barnes said puckishly. Or as puckish as a maimed colonel of dragoons could be.

“If George Louis has any interest whatever in philosophy-for that matter, in anything at all-’tis a secret close kept,” Daniel returned.

“So am I to understand that the present expedition has its origins in a philosophical dispute?” Barnes asked, looking about himself as if seeing the sloop in a new light.

Atalanta had reached the middle of the channel now and, freed from the slow horse-barges, spread more canvas to the wind than she had done before. They were sailing due east on Gravesend Reach. On their right, the chalky hills would draw back from the river, widening the marshes that spread at their feet. The town of Tilbury was on the left. It was the last port on that bank of the river, for beyond it the Thames sloshed between mud-flats instead of streaming between proper banks. Even at their improved pace, they had a few hours’ sail ahead of them; and Isaac was nowhere to be seen. There was no harm, Daniel concluded, in conversing with a philosophy-hobbyist.

He glanced around the sky, looking for a convenient C?lestial Body, but the day had slowly become overcast. Instead he fastened upon the river-water rippling along the hull-planks, and glanced too at the mud-flats below Tilbury. “I cannot see the sun-can you, Colonel Barnes?”