I often think of the Bureau d'Echange de Maux and the wondrously evil old man that sate therein. It stood in a little street that there is in Paris, its doorway made of three brown beams of wood, the top one overlapping the others like the Greek letter pi, all the rest painted green, a house far lower and narrower than its neighbours and infinitely stranger, a thing to take one's fancy. And over the doorway on the old brown beam in faded yellow letters this legend ran, Bureau Universel d'Echanges de Maux.  
I entered at once and accosted the listless man that lolled on a stool by his counter. I demanded the wherefore of his wonderful house, what evil wares he exchanged, with many other things that I wished to know, for curiosity led me; and indeed had it not I had gone at once from that shop, for there was so evil a look in that fattened man, in the hang of his fallen cheeks and his sinful eye, that you would have said he had had dealings with Hell and won the advantage by sheer wickedness.
 
Such a man was mine host; but above all the evil of him lay in his eyes, which lay so still, so apathetic, that you would have sworn that he was drugged or dead; like lizards motionless on a wall they lay, then suddenly they darted, and all his cunning flamed up and revealed itself in what one moment before seemed no more than a sleepy and ordinary wicked old man. And this was the object and trade of that peculiar shop, the Bureau Universel d'Echange de Maux: you paid twenty francs, which the old man proceeded to take from me, for admission to the bureau and then had the right to exchange any evil or misfortune with anyone on the premises for some evil or misfortune that he "could afford," as the old man put it.
 
There were four or five men in the dingy ends of that low-ceilinged room who gesticulated and muttered softly in twos as men who make a bargain, and now and then more came in, and the eyes of the flabby owner of the house leaped up at them as they entered, seemed to know their errands at once and each one's peculiar need, and fell back again into somnolence, receiving his twenty francs in an almost lifeless hand and biting the coin as though in pure absence of mind.
 
"Some of my clients," he told me. So amazing to me was the trade of this extraordinary shop that I engaged the old man in conversation, repulsive though he was, and from his garrulity I gathered these facts. He spoke in perfect English though his utterance was somewhat thick and heavy; no language seemed to come amiss to him. He had been in business a great many years, how many he would not say, and was far older than he looked. All kinds of people did business in his shop. What they exchanged with each other he did not care except that it had to be evils, he was not empowered to carry on any other kind of business.
 
There was no evil, he told me, that was not negotiable there; no evil the old man knew had ever been taken away in despair from his shop. A man might have to wait and come back again next day, and next day and the day after, paying twenty francs each time, but the old man had the addresses of all his clients and shrewdly knew their needs, and soon the right two met and eagerly exchanged their commodities. "Commodities" was the old man's terrible word, said with a gruesome smack of his heavy lips, for he took a pride in his business and evils to him were goods.
 
I learned from him in ten minutes very much of human nature, more than I have ever learned from any other man; I learned from him that a man's own evil is to him the worst thing there is or ever could be, and that an evil so unbalances all men's minds that they always seek for extremes in that small grim shop. A woman that had no children had exchanged with an impoverished half-maddened creature with twelve. On one occasion a man had exchanged wisdom for folly.
 
"Why on earth did he do that?" I said.
 
"None of my business," the old man answered in his heavy indolent way. He merely took his twenty francs from each and ratified the agreement in the little room at the back opening out of the shop where his clients do business. Apparently the man that had parted with wisdom had left the shop upon the tips of his toes with a happy though foolish expression all over his face, but the other went thoughtfully away wearing a troubled and very puzzled look. Almost always it seemed they did business in opposite evils.
 
But the thing that puzzled me most in all my talks with that unwieldy man, the thing that puzzles me still, is that none that had once done business in that shop ever returned again; a man might come day after day for many weeks, but once do business and he never returned; so much the old man told me, but when I asked him why, he only muttered that he ............