supposed to be afloat.  Father Brown, who did not seem to share O’Brien’s sensibilities in the least, went up to the second head and examined it with his blinking care.  It was little more than a mop of wet white hair, fringed with silver fire in the red and level morning light; the face, which seemed of an ugly, empurpled and perhaps criminal type, had been much battered against trees or stones as it tossed in the water.

“Good morning, Commandant O’Brien,” said Valentin, with quiet cordiality.  “You have heard of Brayne’s last experiment in butchery, I suppose?”

Father Brown was still bending over the head with white hair, and he said, without looking up: 

“I suppose it is quite certain that Brayne cut off this head, too.”

“Well, it seems common sense,” said Valentin, with his hands in his pockets.  “Killed in the same way as the other.  Found within a few yards of the other.  And sliced by the same weapon which we know he carried away.”

“Yes, yes; I know,” replied Father Brown submissively.  “Yet, you know, I doubt whether Brayne could have cut off this head.”

“Why not?” inquired Dr. Simon, with a rational stare.

“Well, doctor,” said the priest, looking up blinking, “can a man cut off his own head?  I don’t know.”

O’Brien felt an insane universe crashing about his ears; but the doctor sprang forward with impetuous practicality and pushed back the wet white hair.

“Oh, there’s no doubt it’s Brayne,” said the priest quietly.  “He had exactly that chip in the left ear.”

The detective, who had been regarding the priest with steady and glittering eyes, opened his clenched mouth and said sharply:  “You seem to know a lot about him, Father Brown.”

“I do,” said the little man simply.  “I’ve been about with him for some weeks.  He was thinking of joining our church.”

The star of the fanatic sprang into Valentin’s eyes; he strode towards the priest with clenched hands.  “And, perhaps,” he cried, with a blasting sneer, “perhaps he was also thinking of leaving all his money to your church.”

“Perhaps he was,” said Brown stolidly; “it is possible.”

“In that case,” cried Valentin, with a dreadful smile, “you may indeed know a great deal about him.  About his life and about his—­”

Commandant O’Brien laid a hand on Valentin’s arm.  “Drop that slanderous rubbish, Valentin,” he said, “or there may be more swords yet.”

But Valentin (under the steady, humble gaze of the priest) had already recovered himself.  “Well,” he said shortly, “people’s private opinions can wait.  You gentlemen are still bound by your promise to stay; you must enforce it on yourselves—­and on each other.  Ivan here will tell you anything more you want to know; I must get to business and write to the authorities.  We can’t keep this quiet any longer.  I shall be writing in my study if there is any more news.”