"When Philip lifted his head at last from mending his net he looked rather red, as if sulky or ashamed; but it may have been only the exertion of stooping and the red evening light; I may have only had another of the morbid fancies that seemed to be dancing about me. He merely said gruffly to the man: 'You clear out of this.' And, motioning me to follow, set off wading sh.o.r.eward without paying further attention to him. He stepped on to a stone breakwater that ran out from among the roots of the sand-hills, and so struck homeward, perhaps thinking our incubus would find it less easy to walk on such rough stones, green and slippery with seaweed, than we, who were young and used to it. But my persecutor walked as daintily as he talked; and he still followed me, picking his way and picking his phrases. I heard his delicate, detestable voice appealing to me over my shoulder, until at last, when we had crested the sand-hills, Philip's patience (which was by no means so conspicuous on most occasions) seemed to snap. He turned suddenly, saying, 'Go back. I can't talk to you now.' And as the man hovered and opened his mouth, Philip struck him a buffet on it that sent him flying from the top of the tallest sand-hill to the bottom. I saw him crawling out below, covered with sand.

"This stroke comforted me somehow, though it might well increase my peril; but Philip showed none of his usual elation at his own prowess.

Though as affectionate as ever, he still seemed cast down; and before I could ask him anything fully, he parted with me at his own gate, with two remarks that struck me as strange. He said that, all things considered, I ought to put the coin back in the Collection; but that he himself would keep it 'for the present'. And then he added quite suddenly and irrelevantly: 'You know Giles is back from Australia?'"

The door of the tavern opened and the gigantic shadow of the investigator Flambeau fell across the table. Father Brown presented him to the lady in his own slight, persuasive style of speech, mentioning his knowledge and sympathy in such cases; and almost without knowing, the girl was soon reiterating her story to two listeners. But Flambeau, as he bowed and sat down, handed the priest a small slip of paper. Brown accepted it with some surprise and read on it: "Cab to Wagga Wagga, 379, Mafeking Avenue, Putney." The girl was going on with her story.

"I went up the steep street to my own house with my head in a whirl; it had not begun to clear when I came to the doorstep, on which I found a milk-can--and the man with the twisted nose. The milk-can told me the servants were all out; for, of course, Arthur, browsing about in his brown dressing-gown in a brown study, would not hear or answer a bell.

Thus there was no one to help me in the house, except my brother, whose help must be my ruin. In desperation I thrust two shillings into the horrid thing's hand, and told him to call again in a few days, when I had thought it out. He went off sulking, but more sheepishly than I had expected--perhaps he had been shaken by his fall--and I watched the star of sand splashed on his back receding down the road with a horrid vindictive pleasure. He turned a corner some six houses down.

"Then I let myself in, made myself some tea, and tried to think it out.

I sat at the drawing-room window looking on to the garden, which still glowed with the last full evening light. But I was too distracted and dreamy to look at the lawns and flower-pots and flower-beds with any concentration. So I took the shock the more sharply because I'd seen it so slowly.

"The man or monster I'd sent away was standing quite still in the middle of the garden. Oh, we've all read a lot about pale-faced phantoms in the dark; but this was more dreadful than anything of that kind could ever be. Because, though he cast a long evening shadow, he still stood in warm sunlight. And because his face was not pale, but had that waxen bloom still upon it that belongs to a barber's dummy. He stood quite still, with his face towards me; and I can't tell you how horrid he looked among the tulips and all those tall, gaudy, almost hothouse-looking flowers. It looked as if we'd stuck up a waxwork instead of a statue in the centre of our garden.

"Yet almost the instant he saw me move in the window he turned and ran out of the garden by the back gate, which stood open and by which he had undoubtedly entered. This renewed timidity on his part was so different from the impudence with which he had walked into the sea, that I felt vaguely comforted. I fancied, perhaps, that he feared confronting Arthur more than I knew. Anyhow, I settled down at last, and had a quiet dinner alone (for it was against the rules to disturb Arthur when he was rearranging the museum), and, my thoughts, a little released, fled to Philip and lost themselves, I suppose. Anyhow, I was looking blankly, but rather pleasantly than otherwise, at another window, uncurtained, but by this time black as a slate with the final night-fall. It seemed to me that something like a snail was on the outside of the window-pane.

But when I stared harder, it was more like a man's thumb pressed on the pane; it had that curled look that a thumb has. With my fear and courage re-awakened together, I rushed at the window and then recoiled with a strangled scream that any man but Arthur must have heard.

"For it was not a thumb, any more than it was a snail. It was the tip of a crooked nose, crushed against the gla.s.s; it looked white with the pressure; and the staring face and eyes behind it were at first invisible and afterwards grey like a ghost. I slammed the shutters together somehow, rushed up to my room and locked myself in. But, even as I pa.s.sed, I could swear I saw a second black window with something on it that was like a snail.

"It might be best to go to Arthur after all. If the thing was crawling close all around the house like a cat, it might have purposes worse even than blackmail. My brother might cast me out and curse me for ever, but he was a gentleman, and would defend me on the spot. After ten minutes'

curious thinking, I went down, knocked on the door and then went in: to see the last and worst sight.

"My brother's chair was empty, and he was obviously out. But the man with the crooked nose was sitting waiting for his return, with his hat still insolently on his head, and actually reading one of my brother's books under my brother's lamp. His face was composed and occupied, but his nose-tip still had the air of being the most mobile part of his face, as if it had just turned from left to right like an elephant's proboscis. I had thought him poisonous enough while he was pursuing and watching me; but I think his unconsciousness of my presence was more frightful still.

"I think I screamed loud and long; but that doesn't matter. What I did next does matter: I gave him all the money I had, including a good deal in paper which, though it was mine, I dare say I had no right to touch.

He went off at last, with hateful, tactful regrets all in long words; and I sat down, feeling ruined in every sense. And yet I was saved that very night by a pure accident. Arthur had gone off suddenly to London, as he so often did, for bargains; and returned, late but radiant, having nearly secured a treasure that was an added splendour even to the family Collection. He was so resplendent that I was almost emboldened to confess the abstraction of the lesser gem--, but he bore down all other topics with his over-powering projects. Because the bargain might still misfire any moment, he insisted on my packing at once and going up with him to lodgings he had already taken in Fulham, to be near the curio-shop in question. Thus in spite of myself, I fled from my foe almost in the dead of night--but from Philip also.... My brother was often at the South Kensington Museum, and, in order to make some sort of secondary life for myself, I paid for a few lessons at the Art Schools.

I was coming back from them this evening, when I saw the abomination of desolation walking alive down the long straight street and the rest is as this gentleman has said.

"I've got only one thing to say. I don't deserve to be helped; and I don't question or complain of my punishment; it is just, it ought to have happened. But I still question, with bursting brains, how it can have happened. Am I punished by miracle? or how can anyone but Philip and myself know I gave him a tiny coin in the middle of the sea?"

"It is an extraordinary problem," admitted Flambeau.

"Not so extraordinary as the answer," remarked Father Brown rather gloomily. "Miss Carstairs, will you be at home if we call at your Fulham place in an hour and a half hence?"

The girl looked at him, and then rose and put her gloves on. "Yes," she said, "I'll be there"; and almost instantly left the place.

That night the detective and the priest were still talking of the matter as they drew near the Fulham house, a tenement strangely mean even for a temporary residence of the Carstairs family.

"Of course the superficial, on reflection," said Flambeau, "would think first of this Australian brother who's been in trouble before, who's come back so suddenly and who's just the man to have shabby confederates. But I can't see how he can come into the thing by any process of thought, unless..."

"Well?" asked his companion patiently.

Flambeau lowered his voice. "Unless the girl's lover comes in, too, and he would be the blacker villain. The Australian chap did know that Hawker wanted the coin. But I can't see how on earth he could know that Hawker had got it, unless Hawker signalled to him or his representative across the sh.o.r.e."

"That is true," a.s.sented the priest, with respect.

"Have you noted another thing?" went on Flambeau eagerly, "this Hawker hears his love insulted, but doesn't strike till he's got to the soft sand-hills, where he can be victor in a mere sham-fight. If he'd struck amid rocks and sea, he might have hurt his ally."

"That is true again," said Father Brown, nodding.

"And now, take it from the start. It lies between few people, but at least three. You want one person for suicide; two people for murder; but at least three people for blackmail"

"Why?" asked the priest softly.

"Well, obviously," cried his friend, "there must be one to be exposed; one to threaten exposure; and one at least whom exposure would horrify."

After a long ruminant pause, the priest said: "You miss a logical step.

Three persons are needed as ideas. Only two are needed as agents."

"What can you mean?" asked the other.

"Why shouldn't a blackmailer," asked Brown, in a low voice, "threaten his victim with himself? Suppose a wife became a rigid teetotaller in order to frighten her husband into concealing his pub-frequenting, and then wrote him blackmailing letters in another hand, threatening to tell his wife! Why shouldn't it work? Suppose a father forbade a son to gamble and then, following him in a good disguise, threatened the boy with his own sham paternal strictness! Suppose--but, here we are, my friend."

"My G.o.d!" cried Flambeau; "you don't mean--"

An active figure ran down the steps of the house and showed under the golden lamplight the unmistakable head that resembled the Roman coin.

"Miss Carstairs," said Hawker without ceremony, "wouldn't go in till you came."

"Well," observed Brown confidently, "don't you think it's the best thing she can do to stop outside--with you to look after her? You see, I rather guess you have guessed it all yourself."

"Yes," said the young man, in an undertone, "I guessed on the sands and now I know; that was why I let him fall soft."

Taking a latchkey from the girl and the coin from Hawker, Flambeau let himself and his friend into the empty house and pa.s.sed into the outer parlour. It was empty of all occupants but one. The man whom Father Brown had seen pa.s.s the tavern was standing against the wall as if at bay; unchanged, save that he had taken off his black coat and was wearing a brown dressing-gown.

"We have come," said Father Brown politely, "to give back this coin to its owner." And he handed it to the man with the nose.

Flambeau's eyes rolled. "Is this man a coin-collector?" he asked.

"This man is Mr Arthur Carstairs," said the priest positively, "and he is a coin-collector of a somewhat singular kind."

The man changed colour so horribly that the crooked nose stood out on his face like a separate and comic thing. He spoke, nevertheless, with a sort of despairing dignity. "You shall see, then," he said, "that I have not lost all the family qualities." And he turned suddenly and strode into an inner room, slamming the door.

"Stop him!" shouted Father Brown, bounding and half falling over a chair; and, after a wrench or two, Flambeau had the door open. But it was too late. In dead silence Flambeau strode across and telephoned for doctor and police.

An empty medicine bottle lay on the floor. Across the table the body of the man in the brown dressing-gown lay amid his burst and gaping brown-paper parcels; out of which poured and rolled, not Roman, but very modern English coins.

The priest held up the bronze head of Caesar. "This," he said, "was all that was left of the Carstairs Collection."

After a silence he went on, with more than common gentleness: "It was a cruel will his wicked father made, and you see he did resent it a little. He hated the Roman money he had, and grew fonder of the real money denied him. He not only sold the Collection bit by bit, but sank bit by bit to the basest ways of making money--even to blackmailing his own family in a disguise. He blackmailed his brother from Australia for his little forgotten crime (that is why he took the cab to Wagga Wagga in Putney), he blackmailed his sister for the theft he alone could have noticed. And that, by the way, is why she had that supernatural guess when he was away on the sand-dunes. Mere figure and gait, however distant, are more likely to remind us of somebody than a well-made-up face quite close."

There was another silence. "Well," growled the detective, "and so this great numismatist and coin-collector was nothing but a vulgar miser."

"Is there so great a difference?" asked Father Brown, in the same strange, indulgent tone. "What is there wrong about a miser that is not often as wrong about a collector? What is wrong, except... thou shalt not make to thyself any graven image; thou shalt not bow down to them nor serve them, for I...but we must go and see how the poor young people are getting on."

"I think," said Flambeau, "that in spite of everything, they are probably getting on very well."