A half-light broke through the network of boughs above them, flinging the ghost of a net about their feet; for they were mounting again to the faint luminosity of the naked night.  Flambeau felt truth all round him as an atmosphere, but not as an idea.  He answered with bewildered brain:  “Well, what’s the matter with the sword?  Officers generally have swords, don’t they?”

“They are not often mentioned in modern war,” said the other dispassionately; “but in this affair one falls over the blessed sword everywhere.”

“Well, what is there in that?” growled Flambeau; “it was a twopence coloured sort of incident; the old man’s blade breaking in his last battle.  Anyone might bet the papers would get hold of it, as they have.  On all these tombs and things it’s shown broken at the point.  I hope you haven’t dragged me through this Polar expedition merely because two men with an eye for a picture saw St. Clare’s broken sword.”

“No,” cried Father Brown, with a sharp voice like a pistol shot; “but who saw his unbroken sword?”

“What do you mean?” cried the other, and stood still under the stars.  They had come abruptly out of the grey gates of the wood.

“I say, who saw his unbroken sword?” repeated Father Brown obstinately.  “Not the writer of the diary, anyhow; the general sheathed it in time.”

Flambeau looked about him in the moonlight, as a man struck blind might look in the sun; and his friend went on, for the first time with eagerness: 

“Flambeau,” he cried, “I cannot prove it, even after hunting through the tombs.  But I am sure of it.  Let me add just one more tiny fact that tips the whole thing over.  The colonel, by a strange chance, was one of the first struck by a bullet.  He was struck long before the troops came to close quarters.  But he saw St. Clare’s sword broken.  Why was it broken?  How was it broken?  My friend, it was broken before the battle.”

“Oh!” said his friend, with a sort of forlorn jocularity; “and pray where is the other piece?”

“I can tell you,” said the priest promptly.  “In the northeast corner of the cemetery of the Protestant Cathedral at Belfast.”

“Indeed?” inquired the other.  “Have you looked for it?”

“I couldn’t,” replied Brown, with frank regret.  “There’s a great marble monument on top of it; a monument to the heroic Major Murray, who fell fighting gloriously at the famous Battle of the Black River.”

Flambeau seemed suddenly galvanised into existence.  “You mean,” he cried hoarsely, “that General St. Clare hated Murray, and murdered him on the field of battle because—­”

“You are still full of good and pure thoughts,” said the other.  “It was worse than that.”

“Well,” said the large man, “my stock of evil imagination is used up.”

The priest seemed really doubtful where to begin, and at last he said again: 

“Where would a wise man hide a leaf?  In the forest.”