In his fictional book Sophia House, author Michael O'Brien tells this story:

In the Middle Ages, a famous young painter was hired to create a mural above the high altar of a great church in Paris. The subject was the life of Christ. The artist labored with persistence for many years, and his mural became known as the marvel of its time. Yet it remained incomplete. The artist, try as he might, could not complete two of the faces: the Christ Child and Judas Iscariot. Whenever he attempted to fill in these empty spaces, the results were out of harmony with the rest of the work.

The artist was greatly dissatisfied with the situation and could not understand why, despite his talents, he was unable to bring the mural to completion. He prayed for inspiration daily, and not long afterward, while walking on the streets of the city, he happened upon a group of children playing. Among them was a boy who had the face of an angel and who radiated goodness. The artist invited him to sit as a model of the Christ Child. With his parents' permission the child did, and the finished image was considered a masterpiece. Yet the painter could still find no model for the face of Iscariot.

The story of the artist's quandary spread far and wide throughout the country, and many people, considering themselves the possessors of wicked, deformed, or corrupt faces, offered to pose as the betrayer. But to the artist, none of them seemed quite right for the part. He wanted a face so twisted and ruined by its surrender to depravity that all who gazed upon it would see sin incarnate. Years passed, and the artist would often go to the church to pray for inspiration. He longed to complete the mural, yet in his heart he hoped that the face of Judas would forever elude him, that no human soul would ever be so deeply sunk in sin that it would provide the perfect model.

Then one afternoon as he sat in the church, a beggar staggered down the aisle and knelt at the steps of the altar. He reeked and his clothing hung in rags from his haggard figure. He was not an old man, but he was hunched over, as if weighted by an immense burden of dark memories. His face was exactly what the artist had been looking for. He took the broken man home with him, fed him, washed his diseased flesh, clothed him, and spoke to him warmly, as if with a friend. He instructed his children to treat the visitor with the greatest respect. His wife, a kind and devout woman, prepared fine meals for him. But the poor man dwelt in their midst as if he were made of stone. He was completely unable to speak.

He was, however, willing to sit as the artist's model. Weeks went by, and as the work progressed, the beggar would look from time to time at the image of himself materializing on the canvas. A curious grief and horror would fill his eyes. One day, seeing the model's distress, the artist paused in his labor, laying down his brush.

"My friend," he said, "your heart is troubled. What is it?"

The man buried his face in his hands and burst into tears. After a long moment he lifted his eyes to the old painter. "Do you not remember me?" he said, "Years ago I was your model for the Christ Child."