A low knocking came at the door, which, for some unreasonable reason, curdled everyone's blood like the knocking in Macbeth. Amid that frozen silence Dr. Simon managed to say: "A sabre—yes, I suppose it could."
"Thank you," said Valentin. "Come in, Ivan."
The confidential Ivan opened the door and ushered in Commandant Neil O'Brien, whom he had found at last pacing the garden again.
The Irish officer stood up disordered and defiant on the threshold. "What do you want with me?" he cried.
"Please sit down," said Valentin in pleasant, level tones. "Why, you aren't wearing your sword. Where is it?"
"I left it on the library table," said O'Brien, his brogue deepening in his disturbed mood. "It was a nuisance, it was getting——"
"Ivan," said Valentin, "please go and get the Commandant's sword from the library." Then, as the servant vanished, "Lord Galloway says he saw you leaving the garden just before he found the corpse. What were you doing in the garden?"
The Commandant flung himself recklessly into a chair. "Oh," he cried in pure Irish, "admirin' the moon. Communing with Nature, me bhoy."
A heavy silence sank and endured, and at the end of it came again that trivial and terrible knocking. Ivan reappeared, carrying an empty steel scabbard. "This is all I can find," he said.
"Put it on the table," said Valentin, without looking up.
There was an inhuman silence in the room, like that sea of inhuman silence round the dock of the condemned murderer. The Duchess's weak exclamations had long ago died away. Lord Galloway's swollen hatred was satisfied and even sobered. The voice that came was quite unexpected.
"I think I can tell you," cried Lady Margaret, in that clear, quivering voice with which a courageous woman speaks publicly. "I can tell you what Mr. O'Brien was doing in the garden, since he is bound to silence. He was asking me to marry him. I refused; I said in my family circumstances I could give him nothing but my respect. He was a little angry at that; he did not seem to think much of my respect. I wonder," she added, with rather a wan smile, "if he will care at all for it now. For I offer it him now. I will swear anywhere that he never did a thing like this."
Lord Galloway had edged up to his daughter, and was intimidating her in what he imagined to be an undertone. "Hold your tongue, Maggie," he said in a thunderous whisper. "Why should you shield the fellow? Where's his sword? Where's his confounded cavalry——"
He stopped because of the singular stare with which his daughter was regarding him, a look that was indeed a lurid magnet for the whole group.
"You old fool!" she said in a low voice without pretence of piety, "what do you suppose you are trying to prove? I tell you this man was innocent while with me. But if he wasn't innocent, he was still with me. If he murdered a man in the garden, who was it who must have seen—who must at least have known? Do you hate Neil so much as to put your own daughter——"
Lady Galloway screamed. Everyone else sat tingling at the touch of those satanic tragedies that have been between lovers before now. They saw the proud, white face of the Scotch aristocrat and her lover, the Irish adventurer, like old portraits in a dark house. The long silence was full of formless historical memories of murdered husbands and poisonous paramours.
In the centre of this morbid silence an innocent voice said: "Was it a very long cigar?"
The change of thought was so sharp that they had to look round to see who had spoken.
"I mean," said little Father Brown, from the corner of the room, "I mean that cigar Mr. Brayne is finishing. It seems nearly as long as a walking-stick."
Despite the irrelevance there was assent as well as irritation in Valentin's face as he lifted his head.
"Quite right," he remarked sharply. "Ivan, go and see about Mr. Brayne again, and bring him here at once."
The instant the factotum had closed the door, Valentin addressed the girl with an entirely new earnestness.
"Lady Margaret," he said, "we all feel, I am sure, both gratitude and admiration for your act in rising above your lower dignity and explaining the Commandant's conduct. But there is a hiatus still. Lord Galloway, I understand, met you passing from the study to the drawing-room, and it was only some minutes afterwards that he found the garden and the Commandant still walking there."
"You have to remember," replied Margaret, with a faint irony in her voice, "that I had just refused him, so we should scarcely have come back arm in arm. He is a gentleman, anyhow; and he loitered behind—and so got charged with murder."
"In those few moments," said Valentin gravely, "he might really——"
The knock came again, and Ivan put in his scarred face.
"Beg pardon, sir," he said, "but Mr. Brayne has left the house."
"Left!" cried Valentin, and rose for the first time to his feet.
"Gone. Scooted. Evaporated," replied Ivan in humorous French. "His hat and coat are gone, too, and I'll tell you something to cap it all. I ran outside the house to find any traces of him, and I found one, and a big trace, too."
"What do you mean?" asked Valentin.
"I'll show you," said his servant, and reappeared with a flashing naked cavalry sabre, streaked with blood about the point and edge. Everyone in the room eyed it as if it were a thunderbolt; but the experienced Ivan went on quite quietly:
"I found this," he said, "flung among the bushes fifty yards up the road to Paris. In other words, I found it just where your respectable Mr. Brayne threw it when he ran away."
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