“That may be so; it may also be that the avenger made them vicarious victims.”

“How so?”

“It is human nature.  Did you ever observe a thwarted child striking in its anger the unoffending nurse, destroying its toys to discharge its wrath?  Did you ever see a schoolboy, unable to wreak his anger on the bigger boy who has just struck him, turn against the nearest smaller boy and beat him?  Did you ever know a schoolmaster, angered by one of the boy’s parents, vent his pent-up spleen upon the unoffending class?  Did you ever see a subaltern punished because an officer had been reprimanded?  These are familiar examples of vicarious vengeance.  When the soul is stung to fury, it must solace itself by the discharge of that fury—­it must relieve its pain by the sight of pain in others.  We are so constituted.  We need sympathy above all things.  In joy we cannot bear to see others in distress; in distress we see the joy of others with dismal envy which sharpens our pain.  That is human nature.”

“And,” I exclaimed, carried away by my indignation, “you suppose that the sight of these two happy girls, beaming with the quiet joy of brides, was torture to some miserable wretch who had lost his bride.”

I had gone too far.  His eyes looked into mine.  I read in his that he divined the whole drift of my suspicion—­the allusion made to himself.  There often passes into a look more than words can venture to express.  In that look he read that he was discovered, and I read that he had recognized it.  With perfect calmness, but with a metallic ring in his voice which was like the clash of swords, he said: 

“I did not say that I supposed this; but as we were on the wide field of conjecture—­utterly without evidence one way or the other, having no clue either to the man or his motives—­I drew from the general principles of human nature a conclusion which was just as plausible—­or absurd if you like—­as the conclusion that the motive must have been vanity.”

“As you say, we are utterly without evidence, and conjecture drifts aimlessly from one thing to another.  After all, the most plausible explanation is that of a contagion of imitation.”

I said this in order to cover my previous imprudence.  He was not deceived—­though for a few moments I fancied he was—­but replied: 

“I am not persuaded of that either.  The whole thing is a mystery, and I shall stay here some time in the hope of seeing it cleared up.  Meanwhile, for a subject of conjecture, let me show you something on which your ingenuity may profitably be employed.”

He rose and passed into his bedroom.  I heard him unlocking and rummaging the drawers, and was silently reproaching myself for my want of caution in having spoken as I had done, though it was now beyond all doubt that he was the murderer, and that his motive had been rightly guessed; but with this self-reproach there was mingled a self-gratulation at the way I had got out of the difficulty, as I fancied.