“All right,” assented his friend.  “You tell it.”

Flambeau lifted his head, but lowered his voice.  “General Sir Arthur St. Clare,” he said, “came of a family in which madness was hereditary; and his whole aim was to keep this from his daughter, and even, if possible, from his future son-in-law.  Rightly or wrongly, he thought the final collapse was close, and resolved on suicide.  Yet ordinary suicide would blazon the very idea he dreaded.  As the campaign approached the clouds came thicker on his brain; and at last in a mad moment he sacrificed his public duty to his private.  He rushed rashly into battle, hoping to fall by the first shot.  When he found that he had only attained capture and discredit, the sealed bomb in his brain burst, and he broke his own sword and hanged himself.”

He stared firmly at the grey facade of forest in front of him, with the one black gap in it, like the mouth of the grave, into which their path plunged.  Perhaps something menacing in the road thus suddenly swallowed reinforced his vivid vision of the tragedy, for he shuddered.

“A horrid story,” he said.

“A horrid story,” repeated the priest with bent head.  “But not the real story.”

Then he threw back his head with a sort of despair and cried:  “Oh, I wish it had been.”

The tall Flambeau faced round and stared at him.

“Yours is a clean story,” cried Father Brown, deeply moved. 
“A sweet, pure, honest story, as open and white as that moon. 
Madness and despair are innocent enough.  There are worse things,
Flambeau.”

Flambeau looked up wildly at the moon thus invoked; and from where he stood one black tree-bough curved across it exactly like a devil’s horn.

“Father—­father,” cried Flambeau with the French gesture and stepping yet more rapidly forward, “do you mean it was worse than that?”

“Worse than that,” said Paul like a grave echo.  And they plunged into the black cloister of the woodland, which ran by them in a dim tapestry of trunks, like one of the dark corridors in a dream.

They were soon in the most secret entrails of the wood, and felt close about them foliage that they could not see, when the priest said again: 

“Where does a wise man hide a leaf?  In the forest.  But what does he do if there is no forest?”

“Well, well,” cried Flambeau irritably, “what does he do?”

“He grows a forest to hide it in,” said the priest in an obscure voice.  “A fearful sin.”

“Look here,” cried his friend impatiently, for the dark wood and the dark saying got a little on his nerves; “will you tell me this story or not?  What other evidence is there to go on?”