After he had listened for a minute and a half, he was gripped by a devilish doubt. Perhaps he had dragged the two English policemen to the wastes of a nocturnal heath on an errand no saner than seeking figs on its thistles. For the two priests were talking exactly like priests, piously, with learning and leisure, about the most aerial enigmas of theology. The little Essex priest spoke the more simply, with his round face turned to the strengthening stars; the other talked with his head bowed, as if he were not even worthy to look at them. But no more innocently clerical conversation could have been heard in any white Italian cloister or black Spanish cathedral.

The first he heard was the tail of one of Father Brown's sentences, which ended: "… what they really meant in the Middle Ages by the heavens being incorruptible."

The taller priest nodded his bowed head and said:

"Ah, yes, these modern infidels appeal to their reason; but who can look at those millions of worlds and not feel that there may well be wonderful universes above us where reason is utterly unreasonable?"

"No," said the other priest; "reason is always reasonable, even in the last limbo, in the lost borderland of things. I know that people charge the Church with lowering reason, but it is just the other way. Alone on earth, the Church makes reason really supreme. Alone on earth, the Church affirms that God himself is bound by reason."

The other priest raised his austere face to the spangled sky and said:

"Yet who knows if in that infinite universe—?"

"Only infinite physically," said the little priest, turning sharply in his seat, "not infinite in the sense of escaping from the laws of truth."

Valentin behind his tree was tearing his fingernails with silent fury. He seemed almost to hear the sniggers of the English detectives whom he had brought so far on a fantastic guess only to listen to the metaphysical gossip of two mild old parsons. In his impatience he lost the equally elaborate answer of the tall cleric, and when he listened again it was again Father Brown who was speaking:

"Reason and justice grip the remotest and the loneliest star. Look at those stars. Don't they look as if they were single diamonds and sapphires? Well, you can imagine any mad botany or geology you please. Think of forests of adamant with leaves of brilliants. Think the moon is a blue moon, a single elephantine sapphire. But don't fancy that all that frantic astronomy would make the smallest difference to the reason and justice of conduct. On plains of opal, under cliffs cut out of pearl, you would still find a notice-board, 'Thou shalt not steal.'"

Valentin was just in the act of rising from his rigid and crouching attitude and creeping away as softly as might be, felled by the one great folly of his life. But something in the very silence of the tall priest made him stop until the latter spoke. When at last he did speak, he said simply, his head bowed and his hands on his knees:

"Well, I think that other worlds may perhaps rise higher than our reason. The mystery of heaven is unfathomable, and I for one can only bow my head."

Then, with brow yet bent and without changing by the faintest shade his attitude or voice, he added:

"Just hand over that sapphire cross of yours, will you? We're all alone here, and I could pull you to pieces like a straw doll."

The utterly unaltered voice and attitude added a strange violence to that shocking change of speech. But the guarder of the relic only seemed to turn his head by the smallest section of the compass. He seemed still to have a somewhat foolish face turned to the stars. Perhaps he had not understood. Or, perhaps, he had understood and sat rigid with terror.

"Yes," said the tall priest, in the same low voice and in the same still posture, "yes, I am Flambeau."

Then, after a pause, he said:

"Come, will you give me that cross?"

"No," said the other, and the monosyllable had an odd sound.

Flambeau suddenly flung off all his pontifical pretensions. The great robber leaned back in his seat and laughed low but long.

"No," he cried, "you won't give it me, you proud prelate. You won't give it me, you little celibate simpleton. Shall I tell you why you won't give it me? Because I've got it already in my own breast-pocket."

The small man from Essex turned what seemed to be a dazed face in the dusk, and said, with the timid eagerness of "The Private Secretary":

"Are—are you sure?"

Flambeau yelled with delight.

"Really, you're as good as a three-act farce," he cried. "Yes, you turnip, I am quite sure. I had the sense to make a duplicate of the right parcel, and now, my friend, you've got the duplicate and I've got the jewels. An old dodge, Father Brown—a very old dodge."

"Yes," said Father Brown, and passed his hand through his hair with the same strange vagueness of manner. "Yes, I've heard of it before."

The colossus of crime leaned over to the little rustic priest with a sort of sudden interest.

"You have heard of it?" he asked. "Where have you heard of it?"

"Well, I mustn't tell you his name, of course," said the little man simply. "He was a penitent, you know. He had lived prosperously for about twenty years entirely on duplicate brown paper parcels. And so, you see, when I began to suspect you, I thought of this poor chap's way of doing it at once."

"Began to suspect me?" repeated the outlaw with increased intensity. "Did you really have the gumption to suspect me just because I brought you up to this bare part of the heath?"

"No, no," said Brown with an air of apology. "You see, I suspected you when we first met. It's that little bulge up the sleeve where you people have the spiked bracelet."

"How in Tartarus," cried Flambeau, "did you ever hear of the spiked bracelet?"

"Oh, one's little flock, you know!" said Father Brown, arching his eyebrows rather blankly. "When I was a curate in Hartlepool, there were three of them with spiked bracelets. So, as I suspected you from the first, don't you see, I made sure that the cross should go safe, anyhow. I'm afraid I watched you, you know. So at last I saw you change the parcels. Then, don't you see, I changed them back again. And then I left the right one behind."

"Left it behind?" repeated Flambeau, and for the first time there was another note in his voice beside his triumph.

"Well, it was like this," said the little priest, speaking in the same unaffected way. "I went back to that sweet-shop and asked if I'd left a parcel, and gave them a particular address if it turned up. Well, I knew I hadn't; but when I went away again I did. So, instead of running after me with that valuable parcel, they have sent it flying to a friend of mine in Westminster." Then he added rather sadly: "I learnt that, too, from a poor fellow in Hartlepool. He used to do it with handbags he stole at railway stations, but he's in a monastery now. Oh, one gets to know, you know," he added, rubbing his head again with the same sort of desperate apology. "We can't help being priests. People come and tell us these things."

Flambeau tore a brown-paper parcel out of his inner pocket and rent it in pieces. There was nothing but paper and sticks of lead inside it. He sprang to his feet with a gigantic gesture, and cried:

"I don't believe you. I don't believe a bumpkin like you could manage all that. I believe you've still got the stuff on you, and if you don't give it up—why, we're all alone, and I'll take it by force!"