“He was a friend of mine,” the Doctor continued, with difficulty, “or rather a classmate.  I knew him best at college and afterward—­only slightly.”

“The debt,” Thorpe reminded him, after a pause.  “You were speaking, of his debt to a woman.”

Dexter turned his face away from Thorpe and from the accusing eyes beneath Ralph’s letters.  “She was a very beautiful girl,” he went on, carefully choosing his words, “and they loved each other as people love but once.  My—­my friend was much absorbed in chemistry and had a fondness for original experiment.  She—­the girl, you know—­used to study with him.  He was teaching her and she often helped him in the laboratory.

“They were to be married,” continued Dexter.  “The day before they were to be married, he went to her house and invited her to come to the laboratory to see an experiment which he was trying for the first time and which promised to be unusually interesting.  I need not explain the experiment—­you would not understand.

“On the way to the laboratory, they were talking, as lovers will.  She asked him if he loved her because she was herself; because, of all the women in the world, she was the one God meant for him, or if he loved her because he thought her beautiful.

“He said that he loved her because she was herself, and, most of all, because she was his.  ‘Then,’ she asked, timidly, ’when I am old and all the beauty has gone, you will love me still?  It will be the same, even when I am no longer lovely?’

“He answered her as any man would, never dreaming how soon he was to be tested.

“In the laboratory, they were quite alone.  He began the experiment, explaining as he went, and she watched it as eagerly as he.  He turned away for a moment, to get another chemical.  As he leaned over the retort to put it in, he heard it seethe.  With all her strength, she pushed him away instantly.  There was an explosion which shook the walls of the laboratory, a quantity of deadly gas was released, and, in the fumes, they both fainted.

“When he came to his senses, he learned that she had been terribly burned, and had been taken on the train to the hospital.  He was the one physician in the place and it was the only thing to be done.

“As soon as he could, he went to the hospital.  They told him there that her life would be saved and they hoped for her eyesight, but that she would be permanently and horribly disfigured.  All of her features were destroyed, they said—­she would be only a pitiful wreck of a woman.”

Thorpe was silent.  His blue eyes were dim with pity.  Dexter rose and stood in front of him.  “Do you understand?” he asked, in a voice that was almost unrecognisable.  “His face was close to the retort when she pushed him away.  She saved his life and he went away—­he never saw her again.  He left her without so much as a word.”

“He went away?” asked the minister, incredulously.  “Went away and left her when she had so much to bear?  Deserted her when she needed him to help her bear it, and when she had saved him from death, or worse?”