Except on one point the Galloways were genial and casual enough. So long as Lady Margaret did not take the arm of that adventurer O’Brien, her father was quite satisfied; and she had not done so, she had decorously gone in with Dr. Simon. Nevertheless, old Lord Galloway was restless and almost rude. He was diplomatic enough during dinner, but when, over the cigars, three of the younger men — Simon the doctor, Brown the priest, and the detrimental O’Brien, the exile in a foreign uniform — all melted away to mix with the ladies or smoke in the conservatory, then the English diplomatist grew very undiplomatic indeed. He was stung every sixty seconds with the thought that the scamp O’Brien might be signalling to Margaret somehow; he did not attempt to imagine how. He was left over the coffee with Brayne, the hoary Yankee who believed in all religions, and Valentin, the grizzled Frenchman who believed in none. They could argue with each other, but neither could appeal to him. After a time this “progressive” logomachy had reached a crisis of tedium; Lord Galloway got up also and sought the drawing-room. He lost his way in long passages for some six or eight minutes: till he heard the high-pitched, didactic voice of the doctor, and then the dull voice of the priest, followed by general laughter. They also, he thought with a curse, were probably arguing about “science and religion.” But the instant he opened the salon door he saw only one thing — he saw what was not there. He saw that Commandant O’Brien was absent, and that Lady Margaret was absent too.

  Rising impatiently from the drawing-room, as he had from the dining-room, he stamped along the passage once more. His notion of protecting his daughter from the Irish-Algerian n’er-do-weel had become something central and even mad in his mind. As he went towards the back of the house, where was Valentin’s study, he was surprised to meet his daughter, who swept past with a white, scornful face, which was a second enigma. If she had been with O’Brien, where was O’Brien! If she had not been with O’Brien, where had she been? With a sort of senile and passionate suspicion he groped his way to the dark back parts of the mansion, and eventually found a servants’ entrance that opened on to the garden. The moon with her scimitar had now ripped up and rolled away all the storm-wrack. The argent light lit up all four corners of the garden. A tall figure in blue was striding across the lawn towards the study door; a glint of moonlit silver on his facings picked him out as Commandant O’Brien.

  He vanished through the French windows into the house, leaving Lord Galloway in an indescribable temper, at once virulent and vague. The blue-and-silver garden, like a scene in a theatre, seemed to taunt him with all that tyrannic tenderness against which his worldly authority was at war. The length and grace of the Irishman’s stride enraged him as if he were a rival instead of a father; the moonlight maddened him. He was trapped as if by magic into a garden of troubadours, a Watteau fairyland; and, willing to shake off such amorous imbecilities by speech, he stepped briskly after his enemy. As he did so he tripped over some tree or stone in the grass; looked down at it first with irritation and then a second time with curiosity. The next instant the moon and the tall poplars looked at an unusual sight — an elderly English diplomatist running hard and crying or bellowing as he ran.

  His hoarse shouts brought a pale face to the study door, the beaming glasses and worried brow of Dr. Simon, who heard the nobleman’s first clear words. Lord Galloway was crying: “A corpse in the grass — a blood-stained corpse.” O’Brien at last had gone utterly out of his mind.

  “We must tell Valentin at once,” said the doctor, when the other had brokenly described all that he had dared to examine. “It is fortunate that he is here;” and even as he spoke the great detective entered the study, attracted by the cry. It was almost amusing to note his typical transformation; he had come with the common concern of a host and a gentleman, fearing that some guest or servant was ill. When he was told the gory fact, he turned with all his gravity instantly bright and businesslike; for this, however abrupt and awful, was his business.

  “Strange, gentlemen,” he said as they hurried out into the garden, “that I should have hunted mysteries all over the earth, and now one comes and settles in my own back-yard. But where is the place?” They crossed the lawn less easily, as a slight mist had begun to rise from the river; but under the guidance of the shaken Galloway they found the body sunken in deep grass — the body of a very tall and broad-shouldered man. He lay face downwards, so they could only see that his big shoulders were clad in black cloth, and that his big head was bald, except for a wisp or two of brown hair that clung to his skull like wet seaweed. A scarlet serpent of blood crawled from under his fallen face.

  “At least,” said Simon, with a deep and singular intonation, “he is none of our party.”

  “Examine him, doctor,” cried Valentin rather sharply. “He may not be dead.”

  The doctor bent down. “He is not quite cold, but I am afraid he is dead enough,” he answered. “Just help me to lift him up.”

  They lifted him carefully an inch from the ground, and all doubts as to his being really dead were settled at once and frightfully. The head fell away. It had been entirely sundered from the body; whoever had cut his throat had managed to sever the neck as well. Even Valentin was slightly shocked. “He must have been as strong as a gorilla,” he muttered.

  Not without a shiver, though he was used to anatomical abortions, Dr. Simon lifted the head. It was slightly slashed about the neck and jaw, but the face was substantially unhurt. It was a ponderous, yellow face, at once sunken and swollen, with a hawk-like nose and heavy lids — a face of a wicked Roman emperor, with, perhaps, a distant touch of a Chinese emperor. All present seemed to look at it with the coldest eye of ignorance. Nothing else could be noted about the man except that, as they had lifted his body, they had seen underneath it the white gleam of a shirt-front defaced with a red gleam of blood. As Dr. Simon said, the man had never been of their party. But he might very well have been trying to join it, for he had come dressed for such an occasion.

  Valentin went down on his hands and knees and examined with his closest professional attention the grass and ground for some twenty yards round the body, in which he was assisted less skillfully by the doctor, and quite vaguely by the English lord. Nothing rewarded their grovellings except a few twigs, snapped or chopped into very small lengths, which Valentin lifted for an instant’s examination and then tossed away.

  “Twigs,” he said gravely; “twigs, and a total stranger with his head cut off; that is all there is on this lawn.”

  There was an almost creepy stillness, and then the unnerved Galloway called out sharply:

  “Who’s that! Who’s that over there by the garden wall!”

  A small figure with a foolishly large head drew waveringly near them in the moonlit haze; looked for an instant like a goblin, but turned out to be the harmless little priest whom they had left in the drawing-room.

  “I say,” he said meekly, “there are no gates to this garden, do you know.”

  Valentin’s black brows had come together somewhat crossly, as they did on principle at the sight of the cassock. But he was far too just a man to deny the relevance of the remark. “You are right,” he said. “Before we find out how he came to be killed, we may have to find out how he came to be here. Now listen to me, gentlemen. If it can be done without prejudice to my position and duty, we shall all agree that certain distinguished names might well be kept out of this. There are ladies, gentlemen, and there is a foreign ambassador. If we must mark it down as a crime, then it must be followed up as a crime. But till then I can use my own discretion. I am the head of the police; I am so public that I can afford to be private. Please Heaven, I will clear everyone of my own guests before I call in my men to look for anybody else. Gentlemen, upon your honour, you will none of you leave the house till tomorrow at noon; there are bedrooms for all. Simon, I think you know where to find my man, Ivan, in the front hall; he is a confidential man. Tell him to leave another servant on guard and come to me at once. Lord Galloway, you are certainly the best person to tell the ladies what has happened, and prevent a panic. They also must stay. Father Brown and I will remain with the body.”

  When this spirit of the captain spoke in Valentin he was obeyed like a bugle. Dr. Simon went through to the armoury and routed out Ivan, the public detective’s private detective. Galloway went to the drawing-room and told the terrible news tactfully enough, so that by the time the company assembled there the ladies were already startled and already soothed. Meanwhile the good priest and the good atheist stood at the head and foot of the dead man motionless in the moonlight, like symbolic statues of their two philosophies of death.

  Ivan, the confidential man with the scar and the moustaches, came out of the house like a cannon ball, and came racing across the lawn to Valentin like a dog to his master. His livid face was quite lively with the glow of this domestic detective story, and it was with almost unpleasant eagerness that he asked his master’s permission to examine the remains.

  “Yes; look, if you like, Ivan,” said Valentin, “but don’t be long. We must go in and thrash this out in the house.”

  Ivan lifted the head, and then almost let it drop.

  “Why,” he gasped, “it’s — no, it isn’t; it can’t be. Do you know this man, sir?”

  “No,” said Valentin indifferently; “we had better go inside.”

  Between them they carried the corpse to a sofa in the study, and then all made their way to the drawing-room.

  The detective sat down at a desk quietly, and even without hesitation; but his eye was the iron eye of a judge at assize. He made a few rapid notes upon paper in front of him, and then said shortly: “Is everybody here?”

  “Not Mr. Brayne,” said the Duchess of Mont St. Michel, looking round.

  “No,” said Lord Galloway in a hoarse, harsh voice. “And not Mr. Neil O’Brien, I fancy. I saw that gentleman walking in the garden when the corpse was still warm.”

  “Ivan,” said the detective, “go and fetch Commandant O’Brien and Mr. Brayne. Mr. Brayne, I know, is finishing a cigar in the dining-room; Commandant O’Brien, I think, is walking up and down the conservatory. I am not sure.”

  The faithful attendant flashed from the room, and before anyone could stir or speak Valentin went on with the same soldierly swiftness of exposition.

  “Everyone here knows that a dead man has been found in the garden, his head cut clean from his body. Dr. Simon, you have examined it. Do you think that to cut a man’s throat like that would need great force? Or, perhaps, only a very sharp knife?”

  “I should say that it could not be done with a knife at all,” said the pale doctor.

  “Have you any thought,” resumed Valentin, “of a tool with which it could be done?”

  “Speaking within modern probabilities, I really haven’t,” said the doctor, arching his painful brows. “It’s not easy to hack a neck through even clumsily, and this was a very clean cut. It could be done with a battle-axe or an old headsman’s axe, or an old two-handed sword.”

  “But, good heavens!” cried the Duchess, almost in hysterics, “there aren’t any two-handed swords and battle-axes round here.”

  Valentin was still busy with the paper in front of him. “Tell me,” he said, still writing rapidly, “could it have been done with a long French cavalry sabre?”

  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.