there was a quiver in the very shape of her that was like the lines of an aspen. Merton had sometimes wondered if she had learnt to quail at the crash of the passing trains.
"You see," said Father Brown, blinking modestly, "I'm not sure that the Armstrong cheerfulness is so very cheerful—for other people. You say that nobody could kill such a happy old man, but I'm not sure; ne nos inducas in tentationem. If ever I murdered somebody," he added quite simply, "I dare say it might be an Optimist."
"Why?" cried Merton amused. "Do you think people dislike cheerfulness?"
"People like frequent laughter," answered Father Brown, "but I don't think they like a permanent smile. Cheerfulness without humour is a very trying thing."
They walked some way in silence along the windy grassy bank by the rail, and just as they came under the far-flung shadow of the tall Armstrong house, Father Brown said suddenly, like a man throwing away a troublesome thought rather than offering it seriously: "Of course, drink is neither good nor bad in itself. But I can't help sometimes feeling that men like Armstrong want an occasional glass of wine to sadden them."
Merton's official superior, a grizzled and capable detective named Gilder, was standing on the green bank waiting for the coroner, talking to Patrick Royce, whose big shoulders and bristly beard and hair towered above him. This was the more noticeable because Royce walked always with a sort of powerful stoop, and seemed to be going about his small clerical and domestic duties in a heavy and humbled style, like a buffalo drawing a go-cart.
He raised his head with unusual pleasure at the sight of the priest, and took him a few paces apart. Meanwhile Merton was addressing the older detective respectfully indeed, but not without a certain boyish impatience.
"Well, Mr. Gilder, have you got much farther with the mystery?"
"There is no mystery," replied Gilder, as he looked under dreamy eyelids at the rooks.
"Well, there is for me, at any rate," said Merton, smiling.
"It is simple enough, my boy," observed the senior investigator, stroking his grey, pointed beard. "Three minutes after you'd gone for Mr. Royce's parson the whole thing came out. You know that pasty-faced servant in the black gloves who stopped the train?"
"I should know him anywhere. Somehow he rather gave me the creeps."
"Well," drawled Gilder, "when the train had gone on again, that man had gone too. Rather a cool criminal, don't you think, to escape by the very train that went off for the police?"
"You're pretty sure, I suppose," remarked the young man, "that he really did kill his master?"
"Yes, my son, I'm pretty sure," replied Gilder drily, "for the trifling reason that he has gone off with twenty thousand pounds in papers that were in his master's desk. No, the only thing worth calling a difficulty is how he killed him. The skull seems broken as with some big weapon, but there's no weapon at all lying about, and the murderer would have found it awkward to carry it away, unless the weapon was too small to be noticed."
"Perhaps the weapon was too big to be noticed," said the priest, with an odd little giggle.
Gilder looked round at this wild remark, and rather sternly asked Brown what he meant.
"Silly way of putting it, I know," said Father Brown apologetically. "Sounds like a fairy tale. But poor Armstrong was killed with a giant's club, a great green club, too big to be seen, and which we call the earth. He was broken against this green bank we are standing on."
"How do you mean?" asked the detective quickly.
Father Brown turned his moon face up to the narrow façade of the house and blinked hopelessly up. Following his eyes, they saw that right at the top of this otherwise blind back quarter of the building, an attic window stood open.
"Don't you see," he explained, pointing a little awkwardly like a child, "he was thrown down from there?"
Gilder frowningly scrutinised the window, and then said: "Well, it is certainly possible. But I don't see why you are so sure about it."
Brown opened his grey eyes wide. "Why," he said, "there's a bit of rope round the dead man's leg. Don't you see that other bit of rope up there caught at the corner of the window?"
At that height the thing looked like the faintest particle of dust or hair, but the shrewd old investigator was satisfied. "You're quite right, sir," he said to Father Brown; "that is certainly one to you."
Almost as he spoke a special train with one carriage took the curve of the line on their left, and, stopping, disgorged another group of policemen, in whose midst was the hangdog visage of Magnus, the absconded servant.
"By Jove! they've got him," cried Gilder, and stepped forward with quite a new alertness.
"Have you got the money!" he cried to the first policeman.
The man looked him in the face with a rather curious expression and said: "No." Then he added: "At least, not here."
"Which is the inspector, please?" asked the man called Magnus.
When he spoke everyone instantly understood how this voice had stopped a train. He was a dull-looking man with flat black hair, a colourless face, and a faint suggestion of the East in the level slits in his eyes and mouth. His blood and name, indeed, had remained dubious, ever since Sir Aaron had "rescued" him from a waitership in a London restaurant, and (as some said) from more infamous things. But his voice was as vivid as his face was dead. Whether through exactitude in a foreign language, or in deference to his master (who had been somewhat deaf), Magnus's tones had a peculiarly ringing and piercing quality, and the whole group quite jumped when he spoke.
"I always knew this would happen," he said aloud with brazen blandness. "My poor old master made game of me for wearing black; but I always said I should be ready for his funeral."
And he made a momentary movement with his two dark-gloved hands.
"Sergeant," said Inspector Gilder, eyeing the black hands with wrath, "aren't you putting the bracelets on this fellow; he looks pretty dangerous."
"Well, sir," said the sergeant, with the same odd look of wonder, "I don't know that we can."
"What do you mean?" asked the other sharply. "Haven't you arrested him?"
A faint scorn widened the slit-like mouth, and the whistle of an approaching train seemed oddly to echo the mockery.
"We arrested him," replied the sergeant gravely, "just as he was coming out of the police station at Highgate, where he had deposited all his master's money in the care of Inspector Robinson."
Gilder looked at the man-servant in utter amazement. "Why on earth did you do that?" he asked of Magnus.
"To keep it safe from the criminal, of course," replied that person placidly.
"Surely," said Gilder, "Sir Aaron's money might have been safely left with Sir Aaron's family."
The tail of his sentence was drowned in the roar of the train as it went rocking and clanking; but through all the hell of noises to which that unhappy house was periodically subject, they could hear the syllables of Magnus's answer, in all their bell-like distinctness: "I have no reason to feel confidence in Sir Aaron's family."
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