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 did not know. It was to discover the wherefore of this strange thing and for no other reason at all that I determined myself to do business sooner or later in the little room at the back of that mysterious shop. I determined to exchange some very trivial evil for some evil equally slight, to seek for myself an advantage so very small as scarcely to give Fate as it were a grip, for I deeply distrusted these bargains, knowing well that man has never yet benefited by the marvellous and that the more miraculous his advantage appears to be the more securely and tightly do the gods or the witches catch him. In a few days more I was going back to England and I was beginning to fear that I should be sea-sick: this fear of sea-sickness, not the actual malady but only the mere fear of it, I decided to exchange for a suitably little evil. I did not know with whom I should be dealing, who in reality was the head of the firm (one never does when shopping) but I decided that neither Jew nor Devil could make very much on so small a bargain as that.