To my extreme annoyance, Poirot was not in, and the old Belgian who answered my knock informed me that he believed he had gone to London.

I was dumbfounded. What on earth could Poirot be doing in London! Was it a sudden decision on his part, or had he already made up his mind when he parted from me a few hours earlier?

I retraced my steps to Styles in some annoyance. With Poirot away, I was uncertain how to act. Had he foreseen this arrest? Had he not, in all probability, been the cause of it? Those questions I could not resolve. But in the meantime what was I to do? Should I announce the arrest openly at Styles, or not? Though I did not acknowledge it to myself, the thought of Mary Cavendish was weighing on me. Would it not be a terrible shock to her? For the moment, I set aside utterly any suspicions of her. She could not be implicated—otherwise I should have heard some hint of it.

Of course, there was no possibility of being able permanently to conceal Dr. Bauerstein's arrest from her. It would be announced in every newspaper on the morrow. Still, I shrank from blurting it out. If only Poirot had been accessible, I could have asked his advice. What possessed him to go posting off to London in this unaccountable way?

In spite of myself, my opinion of his sagacity was immeasurably heightened. I would never have dreamt of suspecting the doctor, had not Poirot put it into my head. Yes, decidedly, the little man was clever.

After some reflecting, I decided to take John into my confidence, and leave him to make the matter public or not, as he thought fit.

He gave vent to a prodigious whistle, as I imparted the news.

"Great Scot! You were right, then. I couldn't believe it at the time."

"No, it is astonishing until you get used to the idea, and see how it makes everything fit in. Now, what are we to do? Of course, it will be generally known to-morrow."

John reflected.

"Never mind," he said at last, "we won't say anything at present. There is no need. As you say, it will be known soon enough."

But to my intense surprise, on getting down early the next morning, and eagerly opening the newspapers, there was not a word about the arrest! There was a column of mere padding about "The Styles Poisoning Case," but nothing further. It was rather inexplicable, but I supposed that, for some reason or other, Japp wished to keep it out of the papers. It worried me just a little, for it suggested the possibility that there might be further arrests to come.

After breakfast, I decided to go down to the village, and see if Poirot had returned yet; but, before I could start, a well-known face blocked one of the windows, and the well-known voice said:

"Bonjour, mon ami!"

"Poirot," I exclaimed, with relief, and seizing him by both hands, I dragged him into the room. "I was never so glad to see anyone. Listen, I have said nothing to anybody but John. Is that right?"

"My friend," replied Poirot, "I do not know what you are talking about."

"Dr. Bauerstein's arrest, of course," I answered impatiently.

"Is Bauerstein arrested, then?"

"Did you not know it?"

"Not the least in the world." But, pausing a moment, he added: "Still, it does not surprise me. After all, we are only four miles from the coast."

"The coast?" I asked, puzzled. "What has that got to do with it?"

Poirot shrugged his shoulders.

"Surely, it is obvious!"

"Not to me. No doubt I am very dense, but I cannot see what the proximity of the coast has got to do with the murder of Mrs. Inglethorp."

"Nothing at all, of course," replied Poirot, smiling. "But we were speaking of the arrest of Dr. Bauerstein."

"Well, he is arrested for the murder of Mrs. Inglethorp——"

"What?" cried Poirot, in apparently lively astonishment. "Dr. Bauerstein arrested for the murder of Mrs. Inglethorp?"

"Yes."

"Impossible! That would be too good a farce! Who told you that, my friend?"

"Well, no one exactly told me," I confessed. "But he is arrested."

"Oh, yes, very likely. But for espionage, mon ami."

"Espionage?" I gasped.

"Precisely."

"Not for poisoning Mrs. Inglethorp?"

"Not unless our friend Japp has taken leave of his senses," replied Poirot placidly.

"But—but I thought you thought so too?"

Poirot gave me one look, which conveyed a wondering pity, and his full sense of the utter absurdity of such an idea.

"Do you mean to say," I asked, slowly adapting myself to the new idea, "that Dr. Bauerstein is a spy?"

Poirot nodded.

"Have you never suspected it?"

"It never entered my head."

"It did not strike you as peculiar that a famous London doctor should bury himself in a little village like this, and should be in the habit of walking about at all hours of the night, fully dressed?"

"No," I confessed, "I never thought of such a thing."

"He is, of course, a German by birth," said Poirot thoughtfully, "though he has practiced so long in this country that nobody thinks of him as anything but an Englishman. He was naturalized about fifteen years ago. A very clever man—a Jew, of course."

"The blackguard!" I cried indignantly.

"Not at all. He is, on the contrary, a patriot. Think what he stands to lose. I admire the man myself."

But I could not look at it in Poirot's philosophical way.

"And this is the man with whom Mrs. Cavendish has been wandering about all over the country!" I cried indignantly.

"Yes. I should fancy he had found her very useful," remarked Poirot. "So long as gossip busied itself in coupling their names together, any other vagaries of the doctor's passed unobserved."

"Then you think he never really cared for her?" I asked eagerly—rather too eagerly, perhaps, under the circumstances.

"That, of course, I cannot say, but—shall I tell you my own private opinion, Hastings?"

"Yes."

"Well, it is this: that Mrs. Cavendish does not care, and never has cared one little jot about Dr. Bauerstein!"

"Do you really think so?" I could not disguise my pleasure.

"I am quite sure of it. And I will tell you why."

"Yes?"

"Because she cares for someone else, mon ami."

"Oh!" What did he mean? In spite of myself, an agreeable warmth spread over me. I am not a vain man where women are concerned, but I remembered certain evidences, too lightly thought of at the time, perhaps, but which certainly seemed to indicate——

My pleasing thoughts were interrupted by the sudden entrance of Miss Howard. She glanced round hastily to make sure there was no one else in the room, and quickly produced an old sheet of brown paper. This she handed to Poirot, murmuring as she did so the cryptic words:

"On top of the wardrobe." Then she hurriedly left the room.

Poirot unfolded the sheet of paper eagerly, and uttered an exclamation of satisfaction. He spread it out on the table.

"Come here, Hastings. Now tell me, what is that initial—J. or L.?"

It was a medium sized sheet of paper, rather dusty, as though it had lain by for some time. But it was the label that was attracting Poirot's attention. At the top, it bore the printed stamp of Messrs. Parkson's, the well-known theatrical costumiers, and it was addressed to "—(the debatable initial) Cavendish, Esq., Styles Court, Styles St. Mary, Essex."

"It might be T., or it might be L.," I said, after studying the thing for a minute or two. "It certainly isn't a J."

"Good," replied Poirot, folding up the paper again. "I, also, am of your way of thinking. It is an L., depend upon it!"

"Where did it come from?" I asked curiously. "Is it important?"

"Moderately so. It confirms a surmise of mine. Having deduced its existence, I set Miss Howard to search for it, and, as you see, she has been successful."

"What did she mean by 'On the top of the wardrobe'?"

"She meant," replied Poirot promptly, "that she found it on top of a wardrobe."

"A funny place for a piece of brown paper," I mused.

"Not at all. The top of a wardrobe is an excellent place for brown paper and cardboard boxes. I have kept them there myself. Neatly arranged, there is nothing to offend the eye."

"Poirot," I asked earnestly, "have you made up your mind about this crime?"

"Yes—that is to say, I believe I know how it was committed."

"Ah!"

"Unfortunately, I have no proof beyond my surmise, unless——" With sudden energy, he caught me by the arm, and whirled me down the hall, calling out in French in his excitement: "Mademoiselle Dorcas, Mademoiselle Dorcas, un moment, s'il vous plaît!"

Dorcas, quite flurried by the noise, came hurrying out of the pantry.

"My good Dorcas, I have an idea—a little idea—if it should prove justified, what magnificent chance! Tell me, on Monday, not Tuesday, Dorcas, but Monday, the day before the tragedy, did anything go wrong with Mrs. Inglethorp's bell?"

Dorcas looked very surprised.

"Yes, sir, now you mention it, it did; though I don't know how you came to hear of it. A mouse, or some such, must have nibbled the wire through. The man came and put it right on Tuesday morning."

With a long drawn exclamation of ecstasy, Poirot led the way back to the morning-room.

"See you, one should not ask for outside proof—no, reason should be enough. But the flesh is weak, it is consolation to find that one is on the right track. Ah, my friend, I am like a giant refreshed. I run! I leap!"

And, in very truth, run and leap he did, gambolling wildly down the stretch of lawn outside the long window.

"What is your remarkable little friend doing?" asked a voice behind me, and I turned to find Mary Cavendish at my elbow. She smiled, and so did I. "What is it all about?"

"Really, I can't tell you. He asked Dorcas some question about a bell, and appeared so delighted with her answer that he is capering about as you see!"

Mary laughed.

"How ridiculous! He's going out of the gate. Isn't he coming back to-day?"

"I don't know. I've given up trying to guess what he'll do next."

"Is he quite mad, Mr. Hastings?"

"I honestly don't know. Sometimes, I feel sure he is as mad as a hatter; and then, just as he is at his maddest, I find there is method in his madness."

"I see."

In spite of her laugh, Mary was looking thoughtful this morning. She seemed grave, almost sad.

It occurred to me that it would be a good opportunity to tackle her on the subject of Cynthia. I began rather tactfully, I thought, but I had not gone far before she stopped me authoritatively.

"You are an excellent advocate, I have no doubt, Mr. Hastings, but in this case your talents are quite thrown away. Cynthia will run no risk of encountering any unkindness from me."

I began to stammer feebly that I hoped she hadn't thought—But again she stopped me, and her words were so unexpected that they quite drove Cynthia, and her troubles, out of my mind.

"Mr. Hastings," she said, "do you think I and my husband are happy together?"

I was considerably taken aback, and murmured something about it's not being my business to think anything of the sort.

"Well," she said quietly, "whether it is your business or not, I will tell you that we are not happy."

I said nothing, for I saw that she had not finished.

She began slowly, walking up and down the room, her head a little bent, and that slim, supple figure of hers swaying gently as she walked. She stopped suddenly, and looked up at me.

"You don't know anything about me, do you?" she asked. "Where I come from, who I was before I married John—anything, in fact? Well, I will tell you. I will make a father confessor of you. You are kind, I think—yes, I am sure you are kind."

Somehow, I was not quite as elated as I might have been. I remembered that Cynthia had begun her confidences in much the same way. Besides, a father confessor should be elderly, it is not at all the role for a young man.

"My father was English," said Mrs. Cavendish, "but my mother was a Russian."

"Ah," I said, "now I understand—"

"Understand what?"

"A hint of something foreign—different—that there has always been about you."

"My mother was very beautiful, I believe. I don't know, because I never saw her. She died when I was quite a little child. I believe there was some tragedy connected with her death—she took an overdose of some sleeping draught by mistake. However that may be, my father was broken-hearted. Shortly afterwards, he went into the Consular Service. Everywhere he went, I went with him. When I was twenty-three, I had been nearly all over the world. It was a splendid life—I loved it."

There was a smile on her face, and her head was thrown back. She seemed living in the memory of those old glad days.

"Then my father died. He left me very badly off. I had to go and live with some old aunts in Yorkshire." She shuddered. "You will understand me when I say that it was a deadly life for a girl brought up as I had been. The narrowness, the deadly monotony of it, almost drove me mad." She paused a minute, and added in a different tone: "And then I met John Cavendish."

"Yes?"

"You can imagine that, from my aunts' point of view, it was a very good match for me. But I can honestly say it was not this fact which weighed with me. No, he was simply a way of escape from the insufferable monotony of my life."

I said nothing, and after a moment, she went on:

"Don't misunderstand me. I was quite honest with him. I told him, what was true, that I liked him very much, that I hoped to come to like him more, but that I was not in any way what the world calls 'in love' with him. He declared that that satisfied him, and so—we were married."

She waited a long time, a little frown had gathered on her forehead. She seemed to be looking back earnestly into those past days.

"I think—I am sure—he cared for me at first. But I suppose we were not well matched. Almost at once, we drifted apart. He—it is not a pleasing thing for my pride, but it is the truth—tired of me very soon." I must have made some murmur of dissent, for she went on quickly: "Oh, yes, he did! Not that it matters now—now that we've come to the parting of the ways."

"What do you mean?"

She answered quietly:

"I mean that I am not going to remain at Styles."

"You and John are not going to live here?"

"John may live here, but I shall not."

"You are going to leave him?"

"Yes."

"But why?"

She paused a long time, and said at last:

"Perhaps—because I want to be—free!"

And, as she spoke, I had a sudden vision of broad spaces, virgin tracts of forests, untrodden lands—and a realization of what freedom would mean to such a nature as Mary Cavendish. I seemed to see her for a moment as she was, a proud wild creature, as untamed by civilization as some shy bird of the hills. A little cry broke from her lips:

"You don't know, you don't know, how this hateful place has been prison to me!"

"I understand," I said, "but—but don't do anything rash."

"Oh, rash!" Her voice mocked at my prudence.

Then suddenly I said a thing I could have bitten out my tongue for:

"You know that Dr. Bauerstein has been arrested?"

An instant coldness passed like a mask over her face, blotting out all expression.

"John was so kind as to break that to me this morning."

"Well, what do you think?" I asked feebly.

"Of what?"

"Of the arrest?"

"What should I think? Apparently he is a German spy; so the gardener had told John."

Her face and voice were absolutely cold and expressionless. Did she care, or did she not?

She moved away a step or two, and fingered one of the flower vases.

"These are quite dead. I must do them again. Would you mind moving—thank you, Mr. Hastings." And she walked quietly past me out of the window, with a cool little nod of dismissal.

No, surely she could not care for Bauerstein. No woman could act her part with that icy unconcern.

Poirot did not make his appearance the following morning, and there was no sign of the Scotland Yard men.

But, at lunch-time, there arrived a new piece of evidence—or rather lack of evidence. We had vainly tried to trace the fourth letter, which Mrs. Inglethorp had written on the evening preceding her death. Our efforts having been in vain, we had abandoned the matter, hoping that it might turn up of itself one day. And this is just what did happen, in the shape of a communication, which arrived by the second post from a firm of French music publishers, acknowledging Mrs. Inglethorp's cheque, and regretting they had been unable to trace a certain series of Russian folksongs. So the last hope of solving the mystery, by means of Mrs. Inglethorp's correspondence on the fatal evening, had to be abandoned.

Just before tea, I strolled down to tell Poirot of the new disappointment, but found, to my annoyance, that he was once more out.

"Gone to London again?"

"Oh, no, monsieur, he has but taken the train to Tadminster. 'To see a young lady's dispensary,' he said."

"Silly ass!" I ejaculated. "I told him Wednesday was the one day she wasn't there! Well, tell him to look us up to-morrow morning, will you?"

"Certainly, monsieur."

But, on the following day, no sign of Poirot. I was getting angry. He was really treating us in the most cavalier fashion.

After lunch, Lawrence drew me aside, and asked if I was going down to see him.

"No, I don't think I shall. He can come up here if he wants to see us."

"Oh!" Lawrence looked indeterminate. Something unusually nervous and excited in his manner roused my curiosity.

"What is it?" I asked. "I could go if there's anything special."

"It's nothing much, but—well, if you are going, will you tell him—" he dropped his voice to a whisper—"I think I've found the extra coffee-cup!"

I had almost forgotten that enigmatical message of Poirot's, but now my curiosity was aroused afresh.

Lawrence would say no more, so I decided that I would descend from my high horse, and once more seek out Poirot at Leastways Cottage.

This time I was received with a smile. Monsieur Poirot was within. Would I mount? I mounted accordingly.

Poirot was sitting by the table, his head buried in his hands. He sprang up at my entrance.

"What is it?" I asked solicitously. "You are not ill, I trust?"

"No, no, not ill. But I decide an affair of great moment."

"Whether to catch the criminal or not?" I asked facetiously.

But, to my great surprise, Poirot nodded gravely.

"'To speak or not to speak,' as your so great Shakespeare says, 'that is the question.'"

I did not trouble to correct the quotation.

"You are not serious, Poirot?"

"I am of the most serious. For the most serious of all things hangs in the balance."

"And that is?"

"A woman's happiness, mon ami," he said gravely.

I did not quite know what to say.

"The moment has come," said Poirot thoughtfully, "and I do not know what to do. For, see you, it is a big stake for which I play. No one but I, Hercule Poirot, would attempt it!" And he tapped himself proudly on the breast.

After pausing a few minutes respectfully, so as not to spoil his effect, I gave him Lawrence's message.

"Aha!" he cried. "So he has found the extra coffee-cup. That is good. He has more intelligence than would appear, this long-faced Monsieur Lawrence of yours!"

I did not myself think very highly of Lawrence's intelligence; but I forebore to contradict Poirot, and gently took him to task for forgetting my instructions as to which were Cynthia's days off.

"It is true. I have the head of a sieve. However, the other young lady was most kind. She was sorry for my disappointment, and showed me everything in the kindest way."

"Oh, well, that's all right, then, and you must go to tea with Cynthia another day."

I told him about the letter.

"I am sorry for that," he said. "I always had hopes of that letter. But no, it was not to be. This affair must all be unravelled from within." He tapped his forehead. "These little grey cells. It is 'up to them'—as you say over here." Then, suddenly, he asked: "Are you a judge of finger-marks, my friend?"

"No," I said, rather surprised, "I know that there are no two finger-marks alike, but that's as far as my science goes."

"Exactly."

He unlocked a little drawer, and took out some photographs which he laid on the table.

"I have numbered them, 1, 2, 3. Will you describe them to me?"

I studied the proofs attentively.

"All greatly magnified, I see. No. 1, I should say, are a man's finger-prints; thumb and first finger. No. 2 are a lady's; they are much smaller, and quite different in every way. No. 3"—I paused for some time—"there seem to be a lot of confused finger-marks, but here, very distinctly, are No. 1's."

"Overlapping the others?"

"Yes."

"You recognize them beyond fail?"

"Oh, yes; they are identical."

Poirot nodded, and gently taking the photographs from me locked them up again.

"I suppose," I said, "that as usual, you are not going to explain?"

"On the contrary. No. 1 were the finger-prints of Monsieur Lawrence. No. 2 were those of Mademoiselle Cynthia. They are not important. I merely obtained them for comparison. No. 3 is a little more complicated."

"Yes?"

"It is, as you see, highly magnified. You may have noticed a sort of blur extending all across the picture. I will not describe to you the special apparatus, dusting powder, etc., which I used. It is a well-known process to the police, and by means of it you can obtain a photograph of the finger-prints of any object in a very short space of time. Well, my friend, you have seen the finger-marks—it remains to tell you the particular object on which they had been left."

"Go on—I am really excited."

"Eh bien! Photo No. 3 represents the highly magnified surface of a tiny bottle in the top poison cupboard of the dispensary in the Red Cross Hospital at Tadminster—which sounds like the house that Jack built!"

"Good heavens!" I exclaimed. "But what were Lawrence Cavendish's finger-marks doing on it? He never went near the poison cupboard the day we were there!"

"Oh, yes, he did!"

"Impossible! We were all together the whole time."

Poirot shook his head.

"No, my friend, there was a moment when you were not all together. There was a moment when you could not have been all together, or it would not have been necessary to call to Monsieur Lawrence to come and join you on the balcony."

"I'd forgotten that," I admitted. "But it was only for a moment."

"Long enough."

"Long enough for what?"

Poirot's smile became rather enigmatical.

"Long enough for a gentleman who had once studied medicine to gratify a very natural interest and curiosity."

Our eyes met. Poirot's were pleasantly vague. He got up and hummed a little tune. I watched him suspiciously.

"Poirot," I said, "what was in this particular little bottle?"

Poirot looked out of the window.

"Hydro-chloride of strychnine," he said, over his shoulder, continuing to hum.

"Good heavens!" I said it quite quietly. I was not surprised. I had expected that answer.

"They use the pure hydro-chloride of strychnine very little—only occasionally for pills. It is the official solution, Liq. Strychnine Hydro-clor. that is used in most medicines. That is why the finger-marks have remained undisturbed since then."

"How did you manage to take this photograph?"

"I dropped my hat from the balcony," explained Poirot simply. "Visitors were not permitted below at that hour, so, in spite of my many apologies, Mademoiselle Cynthia's colleague had to go down and fetch it for me."

"Then you knew what you were going to find?"

"No, not at all. I merely realized that it was possible, from your story, for Monsieur Lawrence to go to the poison cupboard. The possibility had to be confirmed, or eliminated."

"Poirot," I said, "your gaiety does not deceive me. This is a very important discovery."

"I do not know," said Poirot. "But one thing does strike me. No doubt it has struck you too."

"What is that?"

"Why, that there is altogether too much strychnine about this case. This is the third time we run up against it. There was strychnine in Mrs. Inglethorp's tonic. There is the strychnine sold across the counter at Styles St. Mary by Mace. Now we have more strychnine, handled by one of the household. It is confusing; and, as you know, I do not like confusion."

Before I could reply, one of the other Belgians opened the door and stuck his head in.

"There is a lady below, asking for Mr Hastings."

"A lady?"

I jumped up. Poirot followed me down the narrow stairs. Mary Cavendish was standing in the doorway.

"I have been visiting an old woman in the village," she explained, "and as Lawrence told me you were with Monsieur Poirot I thought I would call for you."

"Alas, madame," said Poirot, "I thought you had come to honour me with a visit!"

"I will some day, if you ask me," she promised him, smiling.

"That is well. If you should need a father confessor, madame" —she started ever so slightly—"remember, Papa Poirot is always at your service."

She stared at him for a few minutes, as though seeking to read some deeper meaning into his words. Then she turned abruptly away.

"Come, will you not walk back with us too, Monsieur Poirot?"

"Enchanted, madame."

All the way to Styles, Mary talked fast and feverishly. It struck me that in some way she was nervous of Poirot's eyes.

The weather had broken, and the sharp wind was almost autumnal in its shrewishness. Mary shivered a little, and buttoned her black sports coat closer. The wind through the trees made a mournful noise, like some great giant sighing.

We walked up to the great door of Styles, and at once the knowledge came to us that something was wrong.

Dorcas came running out to meet us. She was crying and wringing her hands. I was aware of other servants huddled together in the background, all eyes and ears.

"Oh, m'am! Oh, m'am! I don't know how to tell you—"

"What is it, Dorcas?" I asked impatiently. "Tell us at once."

"It's those wicked detectives. They've arrested him—they've arrested Mr. Cavendish!"

"Arrested Lawrence?" I gasped.

I saw a strange look come into Dorcas's eyes.

"No, sir. Not Mr. Lawrence—Mr. John."

Behind me, with a wild cry, Mary Cavendish fell heavily against me, and as I turned to catch her I met the quiet triumph in Poirot's eyes.