In the Underground

London:

The cellars ran dark with fear, and black waste water, and rats. Funneled from the drains falling from the streets above, into twisting serpentine tunnels beneath the city, winding back upon itself; an architectural palindrome of brick and copper and steel, all uniform in color. Protected by rubberized knee-boots and breathing apparatus, Kinsey and I waded our way through the intestine of this beast, oily light from our lanterns shading the rats into monsters, and hopefully, edging the monsters into hiding.
Still, Kinsey had his shotgun loaded, on his back. This was science, but there could be dangerous things lurking here all the same. It was unfortunate a shotgun is of little use to the smell --- frightfully appalling.

We had been silent for the last half an hour, save for our progress through the septic water, and the ticking of my pocket-watch amplified when we halted. Water ran somewhere in the distance; the rest, a tomb. At one point we encountered the quite dead corpse of some lowlife, bobbing gently against a grating sloping off to the left. Discretion bade we leave him there. I have no doubt he was not the first nor last to be discarded in such manner, tossed into a storm drain in hopes of a final destination in the river.

"How much deeper should we go for these samples of yours, sir?" Kinsey asked, voice layered and scratchy behind the mask. A small falls from an adjoining tributary crashing over the bricks demanded he shout to be heard.
"Not much, I hope," I said. "I shall need a bath in solvents when I leave this foul place as it is. No, I think we shall know it when we see it."

And we did. The clock had moved perhaps twenty minutes when our path lead us into what can only be called a room, our simple lanterns fain to detect the walls. It was silent as a reservoir here, the air sour and yet with the merest hint of passage. The chamber may be closed, but as I feared something was getting out.
Cautiously, I pursued the walls, curving in sallow brick above my head, coming at last to the furthest south end, where the bricks could be seen to be set into earth, a sickly gray clay, as though the sewers abruptly ended into the side of a hill.
"Hold the light for me, Kinsey. I should like a sample of this." I pulled a vial from my jacket, wrapped in oil-cloth, and with my pen-knife dug a patch of clay about one of the bricks, the size of a man's fingernail, spooned it into the glass and set the cork.
"Most excellent."
"I hope it ends up being what you were seeking, sir," Kinsey said, handing over my lantern.
"Indeed. I trust it shall be most useful."
I had no sooner taken the light when I felt the water ripple must curiously about my calves, and cast about for a reason when Kinsey shouted, "Sir!!"
I turned, into yellow fangs, red eyes, claws, and the shotgun roared into the darkness with both barrels. The creature flew against the wall and into the water with a vile splash, and then the chamber was silent but for the movement on the walls. The air was violently vivisected by gunpowder, lights coruscating in my eyes and ears ringing despite the mask.
Kinsey quickly reloaded, tucking the butt of the rifle beneath his arm. "What in the devil's hell was that?"
I held the lantern aloft, as though that might better inform me. "Fetch a rope, Kinsey," I said. "We had best take this poor creature with us. No more of this life, he might prove useful still. . . . ."