“You did not recognise that?” cried Dickens. He actually stopped in his surprise and swung the lamp in my direction. “That was our own dear Ben Jonson and his ‘On the Famous Voyage,’ written somewhere around the Year of Our Lord 1610, if I am not mistaken.”

“You rarely are,” I muttered.

“Thank you,” said Dickens, completely missing my sarcasm.

“But what did all that verse about Cocytus, Phlegethon, filth, stench, noise, and Charon and Cerebus have to do with Mr Drood?”

“It tells me that a river voyage lies before one or both of us, my dear Wilkie.” The lantern showed the corridor—the “nave” as it were—narrowing ahead towards multiple openings. Transept and apse? Altar screen and rood screen? Shelves of opium-smoking Asian mummies? Or just more foul, bone-filled crypts?

“A river voyage?” I repeated stupidly. I wanted very much to have my laudanum then. And I wished very much that I were at home to have it.

THE “APSE” WAS a circular area of the catacomb set under a dome of stone rising about fifteen feet above the floor. We came to it from the side, as if stepping in from the choir aisle, should this be the layout of an actual cathedral. The “altar” was a massive stone bier much like the one that Hatchery had shifted so far above us now.

“If we are meant to move that,” I said, pointing to the bier, “then our voyage ends here.”

Dickens nodded. “We’re not” was all he said. There was a rotted curtain to the left—perhaps once a tapestry, although all patterns had faded to black and brown in the subterranean darkness over the centuries—partially shielding the bier-altar from the apse-area under the dome. Another, plainer, even more rotted curtain hung against the stone wall to the right of this rude presbytery.

“The rood screen,” said Dickens, pointing with his stick at this second curtain. Still using his cane, he moved the rotted fabric aside to reveal a narrow gap in the wall.

The descent here was much steeper and narrower than anything we had yet seen. The steps were of wood; the tunnel appeared to have been gouged out of soil and stone; there were crude wooden pilings shoring up the sides and ceiling.

“Do you think this is older than the catacombs?” I whispered ahead to Dickens as we carefully descended the steep and winding staircase. “Earlier Christian? Roman? Some sort of Saxon Druidic passage?”

“Hardly. I think this is quite recent, Wilkie. No more than a few years old. Notice that the steps appear to be made from railway timbers. They still show signs of pitch. It is my guess that whoever tunnelled this staircase out, tunnelled up to the catacombs above.”

“Up?” I repeated. “Up from what?”

A second later the stench hit me as surely as if I’d stepped into a rural privy and answered my question. I reached for my handkerchief, only to be reminded once again that Dickens had taken it and used it for other purposes so many dark hours ago.

We emerged into the sewer proper a few minutes later. It was a low, vaulted channel only seven or eight feet across and less than six feet high, the floor of it more oozing mud than flowing liquid, the walls and vaulted ceilings of brick. The stench brought so many tears to my eyes that I had to wipe them in order to be able to see what Dickens’s pale cone of bullseye light illuminated.

I saw that Dickens held another silk handkerchief to his nose and mouth. He had brought two! Rather than use both of his, he had commandeered mine for the corpses of the babies, fully knowing, I was sure, that I would need it later. The anger in me deepened.

“This is as far as I go,” I told him.

Dickens’s large eyes seemed puzzled as he turned to me. “Why, for heaven’s sake, Wilkie? We have come so far.”

“I’m not wading in that,” I said, gesturing angrily at the deep and putrid ooze of the channel.

“Oh, we shan’t have to,” said Dickens. “Do you notice the brick walkway along each side? It’s several inches higher than the foul matter.”

“Foul matter” is what we writers call the manuscripts and written-upon galley pages that the publishers return to us. I wondered if Dickens was making some weak joke.

But the “walkways” were there on each side just as he said, curving out of sight in both directions along the narrow sewer tunnel. But they were hardly sidewalks; the one on our side could not have been more than ten inches wide.

I shook my head, unsure.

Handkerchief still held firmly over his lower face and walking stick now tucked under his arm, Dickens had retrieved a clasp knife from his pocket and quickly made three parallel marks on the crumbling brick where our crude staircase opened into the sewer.

“What is that for?” I asked, knowing the answer as soon as I asked the question. Perhaps the vapours were affecting my higher ratiocinative abilities.

“To find our way back,” he said. Folding the knife, he held it in the lamplight and said irrelevantly, “A gift from my American hosts in Massachusetts during my tour. I’ve found it very useful over the years. Come along; it’s getting late.”

“Why do you think our goal lies in this direction?” I asked as I shuffled behind him to the right along the narrow strip of brick, lowering my head to keep the low arching wall there from knocking my top hat into the muck.

“A guess,” said Dickens. Within minutes we had come to a three-tunnel branching of the sewer. Luckily the channel was narrower there and Dickens hopped across, using his stick to keep his balance. He cut three marks on the corner of the centre channel and made room for me to hop after him.

“Why this channel?” I asked when we were twenty or thirty yards in.

“It seemed wider,” said Dickens. We came to another parting of tunnels. He chose the one to the right and marked his three stripes on the brick.

A hundred yards into this lesser channel and he stopped. I saw on the wall opposite—there was no walkway on that side—a metal candle reflector held up on a spade, its handle buried in the muck, with some sort of round wood-and-wire screen propped against the wall beneath it. A quarter of an inch of tallow candle remained in the reflector.

“What on earth could that be?” I whispered. “To what purpose here?”

“The property of a sewer-hunter,” Dickens replied in conversational tones. “Haven’t you read your Mayhew?”

I had not. Staring at the filth-rimmed pan obviously made for screening, I said, “What in Christ’s name could they be sifting and hunting for in this muck?”

“All those things that we lose into the sewers sooner or later,” said Dickens. “Rings. Coins. Even bones can have their value to those who own nothing.” He poked at the spade and circular sieve with his stick. “Richard Beard illustrated just such an apparatus in Mayhew’s London Labour and the London Poor,” he said. “You really must read it, my dear Wilkie.”

“As soon as we get out of here,” I whispered. It was a promise I planned to honour in the breach.

We moved on, sometimes having to scuttle forward in an almost crouching position as the vaulted ceiling grew lower. For a moment I felt panic when I thought of Hatchery’s little bullseye running out of fuel, but then I remembered the heavy stub of catacomb candle in my left pocket.

“Do you think these are part of Bazalgette’s new sewer system?” I asked sometime later. The only good news in our progress was that the overwhelming power of the stench had all but numbed my sense of smell. I realised that I would have to burn my clothes; a misfortune, since I particularly prized the jacket and waistcoat.

I may have mentioned earlier that Joseph Bazalgette, chief engineer of the Board of Works, had proposed a complex system of new sewers to drain off sewage from the Thames and to embank the mudflats along its shores. The passage of the plan had been expedited by the Great Stink of June 1858, when the work of the House of Commons had been disrupted as the members fled the city. The Main Drainage Works at Crossness had been opened just the previous year, but dozens of miles of main and ancillary sewer projects were proceeding across and beneath the city. The Embankment part of the works was scheduled to be opened just five years hence.