There was a silence.

"Why, then," cried Flambeau, "Pauline was alone when she fell, and it was suicide!"

"She was alone when she fell," said Father Brown, "but it was not suicide."

"Then how did she die?" asked Flambeau impatiently.

"She was murdered."

"But she was alone," objected the detective.

"She was murdered when she was all alone," answered the priest.

All the rest stared at him, but he remained sitting in the same old dejected attitude, with a wrinkle in his round forehead and an appearance of impersonal shame and sorrow; his voice was colourless and sad.

"What I want to know," cried Kalon, with an oath, "is when the police are coming for this bloody and wicked sister. She's killed her flesh and blood; she's robbed me of half a million that was just as sacredly mine as—"

"Come, come, prophet," interrupted Flambeau, with a kind of sneer; "remember that all this world is a cloudland."

The hierophant of the sun-god made an effort to climb back on his pedestal. "It is not the mere money," he cried, "though that would equip the cause throughout the world. It is also my beloved one's wishes. To Pauline all this was holy. In Pauline's eyes—"

Father Brown suddenly sprang erect, so that his chair fell over flat behind him. He was deathly pale, yet he seemed fired with a hope; his eyes shone.

"That's it!" he cried in a clear voice. "That's the way to begin. In Pauline's eyes—"

The tall prophet retreated before the tiny priest in an almost mad disorder. "What do you mean? How dare you?" he cried repeatedly.

"In Pauline's eyes," repeated the priest, his own shining more and more. "Go on—in God's name, go on. The foulest crime the fiends ever prompted feels lighter after confession; and I implore you to confess. Go on, go on—in Pauline's eyes—"

"Let me go, you devil!" thundered Kalon, struggling like a giant in bonds. "Who are you, you cursed spy, to weave your spiders' webs round me, and peep and peer? Let me go."

"Shall I stop him?" asked Flambeau, bounding towards the exit, for Kalon had already thrown the door wide open.

"No; let him pass," said Father Brown, with a strange deep sigh that seemed to come from the depths of the universe. "Let Cain pass by, for he belongs to God."

There was a long-drawn silence in the room when he had left it, which was to Flambeau's fierce wits one long agony of interrogation. Miss Joan Stacey very coolly tidied up the papers on her desk.

"Father," said Flambeau at last, "it is my duty, not my curiosity only—it is my duty to find out, if I can, who committed the crime."

"Which crime?" asked Father Brown.

"The one we are dealing with, of course," replied his impatient friend.

"We are dealing with two crimes," said Brown, "crimes of very different weight—and by very different criminals."

Miss Joan Stacey, having collected and put away her papers, proceeded to lock up her drawer. Father Brown went on, noticing her as little as she noticed him.

"The two crimes," he observed, "were committed against the same weakness of the same person, in a struggle for her money. The author of the larger crime found himself thwarted by the smaller crime; the author of the smaller crime got the money."

"Oh, don't go on like a lecturer," groaned Flambeau; "put it in a few words."

"I can put it in one word," answered his friend.

Miss Joan Stacey skewered her business-like black hat on to her head with a business-like black frown before a little mirror, and, as the conversation proceeded, took her handbag and umbrella in an unhurried style, and left the room.

"The truth is one word, and a short one," said Father Brown. "Pauline Stacey was blind."

"Blind!" repeated Flambeau, and rose slowly to his whole huge stature.

"She was subject to it by blood," Brown proceeded. "Her sister would have started eyeglasses if Pauline would have let her; but it was her special philosophy or fad that one must not encourage such diseases by yielding to them. She would not admit the cloud; or she tried to dispel it by will. So her eyes got worse and worse with straining; but the worst strain was to come. It came with this precious prophet, or whatever he calls himself, who taught her to stare at the hot sun with the naked eye. It was called accepting Apollo. Oh, if these new pagans would only be old pagans, they would be a little wiser! The old pagans knew that mere naked Nature-worship must have a cruel side. They knew that the eye of Apollo can blast and blind."

There was a pause, and the priest went on in a gentle and even broken voice. "Whether or no that devil deliberately made her blind, there is no doubt that he deliberately killed her through her blindness. The very simplicity of the crime is sickening. You know he and she went up and down in those lifts without official help; you know also how smoothly and silently the lifts slide. Kalon brought the lift to the girl's landing, and saw her, through the open door, writing in her slow, sightless way the will she had promised him. He called out to her cheerily that he had the lift ready for her, and she was to come out when she was ready. Then he pressed a button and shot soundlessly up to his own floor, walked through his own office, out on to his own balcony, and was safely praying before the crowded street when the poor girl, having finished her work, ran gaily out to where lover and lift were to receive her, and stepped—"

"Don't!" cried Flambeau.

"He ought to have got half a million by pressing that button," continued the little father, in the colourless voice in which he talked of such horrors. "But that went smash. It went smash because there happened to be another person who also wanted the money, and who also knew the secret about poor Pauline's sight. There was one thing about that will that I think nobody noticed: although it was unfinished and without signature, the other Miss Stacey and some servant of hers had already signed it as witnesses. Joan had signed first, saying Pauline could finish it later, with a typical feminine contempt for legal forms. Therefore, Joan wanted her sister to sign the will without real witnesses. Why? I thought of the blindness, and felt sure she had wanted Pauline to sign in solitude because she had wanted her not to sign at all.

"People like the Staceys always use fountain pens; but this was specially natural to Pauline. By habit and her strong will and memory she could still write almost as well as if she saw; but she could not tell when her pen needed dipping. Therefore, her fountain pens were carefully filled by her sister—all except this fountain pen. This was carefully not filled by her sister; the remains of the ink held out for a few lines and then failed altogether. And the prophet lost five hundred thousand pounds and committed one of the most brutal and brilliant murders in human history for nothing."

Flambeau went to the open door and heard the official police ascending the stairs. He turned and said: "You must have followed everything devilish close to have traced the crime to Kalon in ten minutes."

Father Brown gave a sort of start.

"Oh! to him," he said. "No; I had to follow rather close to find out about Miss Joan and the fountain pen. But I knew Kalon was the criminal before I came into the front door."

"You must be joking!" cried Flambeau.

"I'm quite serious," answered the priest. "I tell you I knew he had done it, even before I knew what he had done."