There was again a silence, but of a new sort.  Valentin took the sabre, examined it, reflected with unaffected concentration of thought, and then turned a respectful face to O’Brien.  “Commandant,” he said, “we trust you will always produce this weapon if it is wanted for police examination.  Meanwhile,” he added, slapping the steel back in the ringing scabbard, “let me return you your sword.”

At the military symbolism of the action the audience could hardly refrain from applause.

For Neil O’Brien, indeed, that gesture was the turning-point of existence.  By the time he was wandering in the mysterious garden again in the colours of the morning the tragic futility of his ordinary mien had fallen from him; he was a man with many reasons for happiness.  Lord Galloway was a gentleman, and had offered him an apology.  Lady Margaret was something better than a lady, a woman at least, and had perhaps given him something better than an apology, as they drifted among the old flowerbeds before breakfast.  The whole company was more lighthearted and humane, for though the riddle of the death remained, the load of suspicion was lifted off them all, and sent flying off to Paris with the strange millionaire—­a man they hardly knew.  The devil was cast out of the house—­he had cast himself out.

Still, the riddle remained; and when O’Brien threw himself on a garden seat beside Dr. Simon, that keenly scientific person at once resumed it.  He did not get much talk out of O’Brien, whose thoughts were on pleasanter things.

“I can’t say it interests me much,” said the Irishman frankly, “especially as it seems pretty plain now.  Apparently Brayne hated this stranger for some reason; lured him into the garden, and killed him with my sword.  Then he fled to the city, tossing the sword away as he went.  By the way, Ivan tells me the dead man had a Yankee dollar in his pocket.  So he was a countryman of Brayne’s, and that seems to clinch it.  I don’t see any difficulties about the business.”

“There are five colossal difficulties,” said the doctor quietly; “like high walls within walls.  Don’t mistake me.  I don’t doubt that Brayne did it; his flight, I fancy, proves that.  But as to how he did it.  First difficulty:  Why should a man kill another man with a great hulking sabre, when he can almost kill him with a pocket knife and put it back in his pocket?  Second difficulty:  Why was there no noise or outcry?  Does a man commonly see another come up waving a scimitar and offer no remarks?  Third difficulty:  A servant watched the front door all the evening; and a rat cannot get into Valentin’s garden anywhere.  How did the dead man get into the garden?  Fourth difficulty:  Given the same conditions, how did Brayne get out of the garden?”

“And the fifth,” said Neil, with eyes fixed on the English priest who was coming slowly up the path.

“Is a trifle, I suppose,” said the doctor, “but I think an odd one.  When I first saw how the head had been slashed, I supposed the assassin had struck more than once.  But on examination I found many cuts across the truncated section; in other words, they were struck after the head was off.  Did Brayne hate his foe so fiendishly that he stood sabring his body in the moonlight?”