He looked at Philip through his cigarette smoke as if expecting a reply, but Philip only wet his lips, and remained silent.

“I got six months’ leave of absence,” he resumed, “and set out to see the results of my experiments.  First I went to Rio, and from there to the place where the first couple had gone.  As a consequence, five weeks passed between the date of the last letters of my experimenters and the day I joined them.  Heavens, man!  When I made it known that I wanted them, where do you think they took me?”

He dropped his half-burned cigarette and his voice was husky as he turned on Philip.  “Where—­where do you think they took me?” he demanded.

“God knows!” exclaimed Philip, tremulously.  “Where?”

“To two freshly made graves just outside the village,” groaned the doctor.  “I learned their story after a little.  The girl, finding herself useless there, had begun to teach the little children.  I’m—­I’m—­going to skip quickly over this.”  His voice broke to a whisper.  “She was an angel.  The poor half-naked women told me that through my interpreter.  The children cried for her when she died.  The men had brought flowering trees from miles away to shade her grave—­and the other.  They had met, as I had planned—­the man and the girl, but it didn’t turn out—­my way.  It was a beautiful love, I believe, as pure and sweet as any in the whole world.  They say that they made the whole village happy, and that each Sunday the girl and the man would sing to them beautiful songs which they could not understand, but which made even the sick smile with happiness.  It was a low, villainous place for a village, half encircled by a swampy river, and the terrible heat of the summer sun brought with it a strange sickness.  It was a deadly, fatal sickness, and many died, and always there were the man and the girl, working and singing and striving to do good through all the hours of day and night.  What need is there of saying more?” the doctor cried, his voice choking him.  “What need to say more—­except that the man went first, and that the girl died a week later, and that they were buried side by side under the mangum trees?  What need—­unless it is to say that I am their murderer?”

“There have been many mistakes made in the name of science,” said Philip, clearing his throat.  “This was one.  Your theory was wrong.”

“Yes, it was wrong,” said the doctor, more gently.  “I saved myself by killing them.  My theory died with them, and as fast as I could travel I hurried to that other place in Central America.”

A soft glow entered into his eyes now, and he came around the stove and took one of Philip’s hands between his own, and looked steadily down into his face, while there came a curious twitching about the muscles of his throat.