We had by this time rounded the Halles, and were threading our way through one gloomy by-street after another.  The air was chill, the sky low and rainy; and already the yellow glow of an oil-lamp might be seen gleaming through the inner darkness of some of the smaller shops.  Meanwhile, the dusk seemed to gather at our heels, and to thicken at every step.

“You are sure you know your way?” I asked presently, seeing Mueller look up at the name at the corner of the street.

“Why, yes; I think I do,” he answered, doubtfully.

“Why not inquire of that man just ahead?” I suggested.

He was a square-built, burly, shabby-looking fellow, and was striding along so fast that we had to quicken our pace in order to come up with him.  All at once Mueller fell back, laid his hand on my arm, and said:—­

“Stop!  It is Guichet himself.  Let him go on, and we’ll follow.”

So we dropped into the rear and followed him.  He turned presently to the right, and preceded us down a long and horribly ill-favored street, full of mean cabarets and lodging-houses of the poorest class, where, painted in red letters on broken lamps above the doors, or printed on cards wafered against the window-panes, one saw at almost every other house, the words, “Ici on loge la nuit.”  At the end of this thoroughfare our unconscious guide plunged into a still darker and fouler impasse, hung across from side to side with rows of dingy linen, and ornamented in the centre with a mound of decaying cabbage-leaves, potato-parings, oyster-shells, and the like.  Here he made for a large tumble-down house that closed the alley at the farther end, and, still followed by ourselves, went in at an open doorway, and up a public staircase dimly lighted by a flickering oil-lamp at every landing.  At his own door he paused, and just as he had turned the key, Mueller accosted him.

“Is that you, Guichet?” he said.  “Why, you are the very man I want!  If I had come ten minutes sooner, I should have missed you.”

“Is it M’sieur Mueller?” said Guichet, bending his heavy brows and staring at us in the gloom of the landing.

“Ay, and with me the friend you saw the other day.  So, this is your den?  May we come in?”

He had been standing till now with his hand on the key and the closed door at his back, evidently not intending to admit us; but thus asked, he pushed the door open, and said, somewhat ungraciously:—­

“It is just that, M’sieur Mueller—­a den; not fit for gentlemen like you.  But you can go in, if you please.”