“That is all right,” he said, panting and in halting English.  “I have insulted.  I will give satisfaction.  Marco, open the case.”

The man beside him with the earrings and the big black case proceeded to unlock it.  He took out of it two long Italian rapiers, with splendid steel hilts and blades, which he planted point downwards in the lawn.  The strange young man standing facing the entrance with his yellow and vindictive face, the two swords standing up in the turf like two crosses in a cemetery, and the line of the ranked towers behind, gave it all an odd appearance of being some barbaric court of justice.  But everything else was unchanged, so sudden had been the interruption.  The sunset gold still glowed on the lawn, and the bittern still boomed as announcing some small but dreadful destiny.

“Prince Saradine,” said the man called Antonelli, “when I was an infant in the cradle you killed my father and stole my mother; my father was the more fortunate.  You did not kill him fairly, as I am going to kill you.  You and my wicked mother took him driving to a lonely pass in Sicily, flung him down a cliff, and went on your way.  I could imitate you if I chose, but imitating you is too vile.  I have followed you all over the world, and you have always fled from me.  But this is the end of the world—­and of you.  I have you now, and I give you the chance you never gave my father.  Choose one of those swords.”

Prince Saradine, with contracted brows, seemed to hesitate a moment, but his ears were still singing with the blow, and he sprang forward and snatched at one of the hilts.  Father Brown had also sprung forward, striving to compose the dispute; but he soon found his personal presence made matters worse.  Saradine was a French freemason and a fierce atheist, and a priest moved him by the law of contraries.  And for the other man neither priest nor layman moved him at all.  This young man with the Bonaparte face and the brown eyes was something far sterner than a puritan—­a pagan.  He was a simple slayer from the morning of the earth; a man of the stone age—­a man of stone.

One hope remained, the summoning of the household; and Father Brown ran back into the house.  He found, however, that all the under servants had been given a holiday ashore by the autocrat Paul, and that only the sombre Mrs. Anthony moved uneasily about the long rooms.  But the moment she turned a ghastly face upon him, he resolved one of the riddles of the house of mirrors.  The heavy brown eyes of Antonelli were the heavy brown eyes of Mrs. Anthony; and in a flash he saw half the story.

“Your son is outside,” he said without wasting words; “either he or the prince will be killed.  Where is Mr. Paul?”

“He is at the landing-stage,” said the woman faintly.  “He is —­he is—­signalling for help.”

“Mrs. Anthony,” said Father Brown seriously, “there is no time for nonsense.  My friend has his boat down the river fishing.  Your son’s boat is guarded by your son’s men.  There is only this one canoe; what is Mr. Paul doing with it?”