Not everywhere, mind. The figure knew exactly what it wanted. He started at the face, unclenching the woman’s jaws, wedging open her mouth; then, with gloved fingers pulled out the tongue as though to cut it off at its roots, only to run the blade along its underside, taking shavings of the Soot trapped there, more liquid than powder, then transferring it into the jar by sliding the blade along the inside of its rim, the way you’d clean a butter knife of jam. The sound of steel on glass. It seemed louder than the crowd outside.

I watched all this silently, lying on my stomach, afraid not of the knife but of this man with a dead woman’s tongue between his fingers. He harvested Soot from two more places, the depth of both armpits, then (I turned away here: London’s Smoke in my brain and lungs, and still I turned away, could not bear it, was ashamed) from the scissor of her thighs: scraped the knife again and again against the rim of his glass, then screwed it tightly shut. All told it took him no more than a few minutes. He never turned around, worked with precision, never more quickly than the task merited, but with an efficiency that hinted at practice.

Then the light changed, down in this coffin that formed the base of London’s gallows, grew darker. It was the face and upper body of the executioner bending over the trapdoor and thus blocking much of its light. He did not say anything, but I saw the figure nod to him and pocket its jar. Immediately, the executioner rose again, barked an order at the guards, to fetch the cadaver.

I had but one thought now, and that was to crawl back out. I moved, rolled back towards the canvas flap I had pried loose. I turned once before pushing through. The figure was at the opposite side, crouching in front of a little door that served as its exit. He, too, turned. It was dark, and it was smoky, and yet I swear we would recognise one another again. An odd face, lined and old but also boyish, the chin closely shaved under a bloom of whiskers, with a fine, bony nose and graceful eyebrows; large, heavy-hooded eyes. A gentleman’s face, I remember thinking; or a gentle-born boy’s who’s been aged in his sleep. Like an evil Snow White. Then the man stepped out, closing the door, and I rolled through into the street, where the vomit jumped out of me like a living thing that wanted to get out, out, out, as though association with my body was shameful even for my half-digested dregs of breakfast.