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:

"Bon jour, 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 some one 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 plait!"

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............