policeman and induced him to stand opposite the entrance and watch it; and finally paused an instant for a pennyworth of chestnuts, and an inquiry as to the probable length of the merchant's stay in the neighbourhood.
The chestnut seller, turning up the collar of his coat, told him he should probably be moving shortly, as he thought it was going to snow. Indeed, the evening was growing grey and bitter, but Angus, with all his eloquence, proceeded to nail the chestnut man to his post.
"Keep yourself warm on your own chestnuts," he said earnestly. "Eat up your whole stock; I'll make it worth your while. I'll give you a sovereign if you'll wait here till I come back, and then tell me whether any man, woman, or child has gone into that house where the commissionaire is standing."
He then walked away smartly, with a last look at the besieged tower.
"I've made a ring round that room, anyhow," he said. "They can't all four of them be Mr. Welkin's accomplices."
Lucknow Mansions were, so to speak, on a lower platform of that hill of houses, of which Himylaya Mansions might be called the peak. Mr. Flambeau's semi-official flat was on the ground floor, and presented in every way a marked contrast to the American machinery and cold hotel-like luxury of the flat of the Silent Service. Flambeau, who was a friend of Angus, received him in a rococo artistic den behind his office, of which the ornaments were sabres, harquebuses, Eastern curiosities, flasks of Italian wine, savage cooking-pots, a plumy Persian cat, and a small dusty-looking Roman Catholic priest, who looked particularly out of place.
"This is my friend Father Brown," said Flambeau. "I've often wanted you to meet him. Splendid weather, this; a little cold for Southerners like me."
"Yes, I think it will keep clear," said Angus, sitting down on a violet-striped Eastern ottoman.
"No," said the priest quietly, "it has begun to snow."
And, indeed, as he spoke, the first few flakes, foreseen by the man of chestnuts, began to drift across the darkening windowpane.
"Well," said Angus heavily. "I'm afraid I've come on business, and rather jumpy business at that. The fact is, Flambeau, within a stone's throw of your house is a fellow who badly wants your help; he's perpetually being haunted and threatened by an invisible enemy—a scoundrel whom nobody has even seen." As Angus proceeded to tell the whole tale of Smythe and Welkin, beginning with Laura's story, and going on with his own, the supernatural laugh at the corner of two empty streets, the strange distinct words spoken in an empty room, Flambeau grew more and more vividly concerned, and the little priest seemed to be left out of it, like a piece of furniture. When it came to the scribbled stamp-paper pasted on the window, Flambeau rose, seeming to fill the room with his huge shoulders.
"If you don't mind," he said, "I think you had better tell me the rest on the nearest road to this man's house. It strikes me, somehow, that there is no time to be lost."
"Delighted," said Angus, rising also, "though he's safe enough for the present, for I've set four men to watch the only hole to his burrow."
They turned out into the street, the small priest trundling after them with the docility of a small dog. He merely said, in a cheerful way, like one making conversation, "How quick the snow gets thick on the ground."
As they threaded the steep side streets already powdered with silver, Angus finished his story; and by the time they reached the crescent with the towering flats, he had leisure to turn his attention to the four sentinels. The chestnut seller, both before and after receiving a sovereign, swore stubbornly that he had watched the door and seen no visitor enter. The policeman was even more emphatic. He said he had had experience of crooks of all kinds, in top hats and in rags; he wasn't so green as to expect suspicious characters to look suspicious; he looked out for anybody, and, so help him, there had been nobody. And when all three men gathered round the gilded commissionaire, who still stood smiling astride of the porch, the verdict was more final still.
"I've got a right to ask any man, duke or dustman, what he wants in these flats," said the genial and gold-laced giant, "and I'll swear there's been nobody to ask since this gentleman went away."
The unimportant Father Brown, who stood back, looking modestly at the pavement, here ventured to say meekly, "Has nobody been up and down stairs, then, since the snow began to fall? It began while we were all round at Flambeau's."
"Nobody's been in here, sir, you can take it from me," said the official, with beaming authority.
"Then I wonder what that is?" said the priest, and stared at the ground blankly like a fish.
The others all looked down also; and Flambeau used a fierce exclamation and a French gesture. For it was unquestionably true that down the middle of the entrance guarded by the man in gold lace, actually between the arrogant, stretched legs of that colossus, ran a stringy pattern of grey footprints stamped upon the white snow.
"God!" cried Angus involuntarily, "the Invisible Man!"
Without another word he turned and dashed up the stairs, with Flambeau following; but Father Brown still stood looking about him in the snow-clad street as if he had lost interest in his query.
Flambeau was plainly in a mood to break down the door with his big shoulders; but the Scotchman, with more reason, if less intuition, fumbled about on the frame of the door till he found the invisible button; and the door swung slowly open.
It showed substantially the same serried interior; the hall had grown darker, though it was still struck here and there with the last crimson shafts of sunset, and one or two of the headless machines had been moved from their places for this or that purpose, and stood here and there about the twilit place. The green and red of their coats were all darkened in the dusk; and their likeness to human shapes slightly increased by their very shapelessness. But in the middle of them all, exactly where the paper with the red ink had lain, there lay something that looked like red ink spilt out of its bottle. But it was not red ink.
With a French combination of reason and violence Flambeau simply said "Murder!" and, plunging into the flat, had explored, every corner and cupboard of it in five minutes. But if he expected to find a corpse he found none. Isidore Smythe was not in the place, either dead or alive. After the most tearing search the two men met each other in the outer hall, with streaming faces and staring eyes. "My friend," said Flambeau, talking French in his excitement, "not only is your murderer invisible, but he makes invisible also the murdered man."
Angus looked round at the dim room full of dummies, and in some Celtic corner of his Scotch soul a shudder started. One of the life-size dolls stood immediately overshadowing the blood stain, summoned, perhaps, by the slain man an instant before he fell. One of the high-shouldered hooks that served the thing for arms, was a little lifted, and Angus had suddenly the horrid fancy that poor Smythe's own iron child had struck him down. Matter had rebelled, and these machines had killed their master. But even so, what had they done with him?
"Eaten him?" said the nightmare at his ear; and he sickened for an instant at the idea of rent, human remains absorbed and crushed into all that acephalous clockwork.
He recovered his mental health by an emphatic effort, and said to Flambeau, "Well, there it is. The poor fellow has evaporated like a cloud and left a red streak on the floor. The tale does not belong to this world."
"There is only one thing to be done," said Flambeau, "whether it belongs to this world or the other. I must go down and talk to my friend."
They descended, passing the man with the pail, who again asseverated that he had let no intruder pass, down to the commissionaire
