“And the lengths the baron went to prove it! Hunting for paintings, letters, diaries. It was quite an obsession with him. ‘None of these accounts mention snow,’ he whispered to me once. ‘It’s changed our climate: all the Smoke in the atmosphere, it’s blocking out the sun.’ At times I feared he had gone mad. Before long I believed it as surely as he. We would sit together and discuss it, night after night.”

Renfrew chuckles at the memory, fondly, Charlie thinks, a man remembering his mentor and friend.

“What if there was though, Mr. Cooper? A time before Smoke. If it came to us in the seventeenth century, as Baron Naylor posits, by land or by sea, from some far-flung corner of this world? What difference does it make?”

Charlie surprises himself by the intensity of his answer. “It means we can fight Smoke. Defeat it.”

Renfrew smiles. It’s a friendly smile but also condescending.

“That’s just what the baron thought. He declared a war on Smoke. A crusade! And threw himself into a frenzy of research, on all manner of fronts: history, archaeology, anatomy. Travelled the world, collecting evidence. Cut open a dozen carcasses, pickling their livers.

“And to what end? To defeat a symptom. The one thing that tells us we are sick. Foolishness. It’s the one thing he never understood. Yes, very well: Smoke has a history. But so does sin! Oh, it did not come to us two hundred and fifty years ago. It’s older than that! Much older. But not”—here Renfrew rises, stands towering over Charlie, steam rising from his china cup—“eternal!”

Charlie looks up at him, takes refuge in ignorance, only half feigned.

“I don’t understand,” he says.

It sets Renfrew to pacing: three steps one way, three steps back. It’s a small cottage, really, and mould blooms richly on one whitewashed wall.

“Remember your Bible, Mr. Cooper. The holy books of the Jews, what we call the Old Testament. Genesis: the tree, the snake, expulsion from Eden. What is this book if not the record of a memory, very ancient, preserved in the form of story? A primitive people making sense of a momentous event in their past. The memory of the coming of sin!

“Sin is a disease. A germ, as some of the Continental scientists would say. Through time, it transformed, became visible to the plain eye, materialised externally. A startling event, no doubt, but one of no consequence; merely a change of symptomology. What we must work on — scientifically, that is, pooling all our knowledge, and not hiding behind an artificial wall like the embargo — is the eradication of the actual disease. I have a scheme, you see. We need to breed it out of society. First out of the gentry. And then. . Until at last, we are all the same.”