POIROT'S abrupt departure had intrigued us all greatly. Sunday morning wore away, and still he did not reappear. But about three o'clock a ferocious and prolonged hooting outside drove us to the window, to see Poirot alighting from a car, accompanied by Japp and Summerhaye. The little man was transformed. He radiated an absurd complacency. He bowed with exaggerated respect to Mary Cavendish.

"Madame, I have your permission to hold a little reunion in the salon? It is necessary for every one to attend."

Mary smiled sadly.

"You know, Monsieur Poirot, that you have carte blanche in every way."

"You are too amiable, madame."

Still beaming, Poirot marshalled us all into the drawing-room, bringing forward chairs as he did so.

"Miss Howard--here. Mademoiselle Cynthia. Monsieur Lawrence. The good Dorcas. And Annie. Bien! We must delay our proceedings a few minutes until Mr. Inglethorp arrives. I have sent him a note."

Miss Howard rose immediately from her seat.

"If that man comes into the house, I leave it!"

"No, no!" Poirot went up to her and pleaded in a low voice.

Finally Miss Howard consented to return to her chair. A few minutes later Alfred Inglethorp entered the room.

The company once assembled, Poirot rose from his seat with the air of a popular lecturer, and bowed politely to his audience.

"Messieurs, mesdames, as you all know, I was called in by Monsieur John Cavendish to investigate this case. I at once examined the bedroom of the deceased which, by the advice of the doctors, had been kept locked, and was consequently exactly as it had been when the tragedy occurred. I found: first, a fragment of green material; second, a stain on the carpet near the window, still damp; thirdly, an empty box of bromide powders.

"To take the fragment of green material first, I found it caught in the bolt of the communicating door between that room and the adjoining one occupied by Mademoiselle Cynthia. I handed the fragment over to the police who did not consider it of much importance. Nor did they recognize it for what it was--a piece torn from a green land armlet."

There was a little stir of excitement.

"Now there was only one person at Styles who worked on the land--Mrs. Cavendish. Therefore it must have been Mrs. Cavendish who entered the deceased's room through the door communicating with Mademoiselle Cynthia's room."

"But that door was bolted on the inside!" I cried.

"When I examined the room, yes. But in the first place we have only her word for it, since it was she who tried that particular door and reported it fastened. In the ensuing confusion she would have had ample opportunity to shoot the bolt across. I took an early opportunity of verifying my conjectures. To begin with, the fragment corresponds exactly with a tear in Mrs. Cavendish's armlet. Also, at the inquest, Mrs. Cavendish declared that she had heard, from her own room, the fall of the table by the bed. I took an early opportunity of testing that statement by stationing my friend Monsieur Hastings in the left wing of the building, just outside Mrs. Cavendish's door. I myself, in company with the police, went to the deceased's room, and whilst there I, apparently accidentally, knocked over the table in question, but found that, as I had expected, Monsieur Hastings had heard no sound at all. This confirmed my belief that Mrs. Cavendish was not speaking the truth when she declared that she had been dressing in her room at the time of the tragedy. In fact, I was convinced that, far from having been in her own room, Mrs. Cavendish was actually in the deceased's room when the alarm was given."

I shot a quick glance at Mary. She was very pale, but smiling.

"I proceeded to reason on that assumption. Mrs. Cavendish is in her mother-in-law's room. We will say that she is seeking for something and has not yet found it. Suddenly Mrs. Inglethorp awakens and is seized with an alarming paroxysm. She flings out her arm, overturning the bed table, and then pulls desperately at the bell. Mrs. Cavendish, startled, drops her candle, scattering the grease on the carpet. She picks it up, and retreats quickly to Mademoiselle Cynthia's room, closing the door behind her. She hurries out into the passage, for the servants must not find her where she is. But it is too late! Already footsteps are echoing along the gallery which connects the two wings. What can she do? Quick as thought, she hurries back to the young girl's room, and starts shaking her awake. The hastily aroused household come trooping down the passage. They are all busily battering at Mrs. Inglethorp's door. It occurs to nobody that Mrs. Cavendish has not arrived with the rest, but--and this is significant--I can find no one who saw her come from the other wing." He looked at Mary Cavendish. "Am I right, madame?"

She bowed her head.

"Quite right, monsieur. You understand that, if I had thought I would do my husband any good by revealing these facts, I would have done so. But it did not seem to me to bear upon the question of his guilt or innocence."

"In a sense, that is correct, madame. But it cleared my mind of many misconceptions, and left me free to see other facts in their true significance."

"The will!" cried Lawrence. "Then it was you, Mary, who destroyed the will?"

She shook her head, and Poirot shook his also.

"No," he said quietly. "There is only one person who could possibly have destroyed that will--Mrs. Inglethorp herself!"

"Impossible!" I exclaimed. "She had only made it out that very afternoon!"

"Nevertheless, mon ami, it was Mrs. Inglethorp. Because, in no other way can you account for the fact that, on one of the hottest days of the year, Mrs. Inglethorp ordered a fire to be lighted in her room."

I gave a gasp. What idiots we had been never to think of that fire as being incongruous! Poirot was continuing:

"The temperature on that day, messieurs, was 80 degrees in the shade. Yet Mrs. Inglethorp ordered a fire! Why? Because she wished to destroy something, and could think of no other way. You will remember that, in consequence of the War economics practiced at Styles, no waste paper was thrown away. There was therefore no means of destroying a thick document such as a will. The moment I heard of a fire being lighted in Mrs. Inglethorp's room, I leaped to the conclusion that it was to destroy some important document--possibly a will. So the discovery of the charred fragment in the grate was no surprise to me. I did not, of course, know at the time that the will in question had only been made this afternoon, and I will admit that, when I learnt that fact, I fell into a grievous error. I came to the conclusion that Mrs. Inglethorp's determination to destroy her will arose as a direct consequence of the quarrel she had that afternoon, and that therefore the quarrel took place after, and not before the making of the will.

"Here, as we know, I was wrong, and I was forced to abandon that idea. I faced the problem from a new standpoint. Now, at 4 o'clock, Dorcas overheard her mistress saying angrily: 'You need not think that any fear of publicity, or scandal between husband and wife will deter me." I conjectured, and conjectured rightly, that these words were addressed, not to her husband, but to Mr. John Cavendish. At 5 o'clock, an hour later, she uses almost the same words, but the standpoint is different. She admits to Dorcas, 'I don't know what to do; scandal between husband and wife is a dreadful thing.' At 4 o'clock she has been angry, but completely mistress of herself. At 5 o'clock she is in violent distress, and speaks of having had a great shock.

"Looking at the matter psychologically, I drew one deduction which I was convinced was correct. The second 'scandal' she spoke of was not the same as the first--and it concerned herself!

"Let us reconstruct. At 4 o'clock, Mrs. Inglethorp quarrels with her son, and threatens to denounce him to his wife--who, by the way, overheard the greater part of the conversation. At 4.30, Mrs. Inglethorp, in consequence of a conversation on the validity of wills, makes a will in favour of her husband, which the two gardeners witness. At 5 o'clock, Dorcas finds her mistress in a state of considerable agitation, with a slip of paper--'a letter,' Dorcas thinks--in her hand, and it is then that she orders the fire in her room to be lighted. Presumably, then, between 4.30 and 5 o'clock, something has occurred to occasion a complete revolution of feeling, since she is now as anxious to destroy the will, as she was before to make it. What was that something?

"As far as we know, she was quite alone during that half-hour. Nobody entered or left that boudoir. What then occasioned this sudden change of sentiment?

"One can only guess, but I believe my guess to be correct. Mrs. Inglethorp had no stamps in her desk. We know this, because later she asked Dorcas to bring her some. Now in the opposite corner of the room stood her husband's desk--locked. She was anxious to find some stamps, and, according to my theory, she tried her own keys in the desk. That one of them fitted I know. She therefore opened the desk, and in searching for the stamps she came across something else--that slip of paper which Dorcas saw in her hand, and which assuredly was never meant for Mrs. Inglethorp's eyes. On the other hand, Mrs. Cavendish believed that the slip of paper to which her mother-in-law clung so tenaciously was a written proof of her own husband's infidelity. She demanded it from Mrs. Inglethorp who assured her, quite truly, that it had nothing to do with that matter. Mrs. Cavendish did not believe her. She thought that Mrs. Inglethorp was shielding her stepson. Now Mrs. Cavendish is a very resolute woman, and, behind her mask of reserve, she was madly jealous of her husband. She determined to get hold of that paper at all costs, and in this resolution chance came to her aid. She happened to pick up the key of Mrs. Inglethorp's despatch-case, which had been lost that morning. She knew that her mother-in-law invariably kept all important papers in this particular case.

"Mrs. Cavendish, therefore, made her plans as only a woman driven desperate through jealousy could have done. Some time in the evening she unbolted the door leading into Mademoiselle Cynthia's room. Possibly she applied oil to the hinges, for I found that it opened quite noiselessly when I tried it. She put off her project until the early hours of the morning as being safer, since the servants were accustomed to hearing her move about her room at that time. She dressed completely in her land kit, and made her way quietly through Mademoiselle Cynthia's room into that of Mrs. Inglethorp."

He paused a moment, and Cynthia interrupted:

"But I should have woken up if anyone had come through my room?"

"Not if you were drugged, mademoiselle."

"Drugged?"

"Mais, oui!"

"You remember"--he addressed us collectively again--"that through all the tumult and noise next door Mademoiselle Cynthia slept. That admitted of two possibilities. Either her sleep was feigned--which I did not believe--or her unconsciousness was indeed by artificial means.

"With this latter idea in my mind, I examined all the coffee-cups most carefully, remembering that it was Mrs. Cavendish who had brought Mademoiselle Cynthia her coffee the night before. I took a sample from each cup, and had them analysed--with no result. I had counted the cups carefully, in the event of one having been removed. Six persons had taken coffee, and six cups were duly found. I had to confess myself mistaken.

"Then I discovered that I had been guilty of a very grave oversight. Coffee had been brought in for seven persons, not six, for Dr. Bauerstein had been there that evening. This changed the face of the whole affair, for there was now one cup missing. The servants noticed nothing, since Annie, the housemaid, who took in the coffee, brought in seven cups, not knowing that Mr. Inglethorp never drank it, whereas Dorcas, who cleared them away the following morning, found six as usual--or strictly speaking she found five, the sixth being the one found broken in Mrs. Inglethorp's room.

"I was confident that the missing cup was that of Mademoiselle Cynthia. I had an additional reason for that belief in the fact that all the cups found contained sugar, which Mademoiselle Cynthia never took in her coffee. My attention was attracted by the story of Annie about some 'salt' on the tray of coco which she took every night to Mrs. Inglethorp's room. I accordingly secured a sample of that coco, and sent it to be analysed."

"But that had already been done by Dr. Bauerstein," said Lawrence quickly.

"Not exactly. The analyst was asked by him to report whether strychnine was, or was not, present. He did not have it tested, as I did, for a narcotic."

"For a narcotic?"

"Yes. Here is the analyst's report. Mrs. Cavendish administered a safe, but effectual, narcotic to both Mrs. Inglethorp and Mademoiselle Cynthia. And it is possible that she had a mauvais quart d'heure in consequence! Imagine her feelings when her mother-in-law is suddenly taken ill and dies, and immediately after she hears the word 'Poison'! She has believed that the sleeping draught she administered was perfectly harmless, but there is no doubt that for one terrible moment she must have feared that Mrs. Inglethorp's death lay at her door. She is seized with panic, and under its influence she hurries downstairs, and quickly drops the coffee-cup and saucer used by Mademoiselle Cynthia into a large brass vase, where it is discovered later by Monsieur Lawrence. The remains of the coco she dare not touch. Too many eyes are upon her. Guess at her relief when strychnine is mentioned, and she discovers that after all the tragedy is not her doing.

"We are now able to account for the symptoms of strychnine poisoning being so long in making their appearance. A narcotic taken with strychnine will delay the action of the poison for some hours."

Poirot paused. Mary looked up at him, the colour slowly rising in her face.

"All you have said is quite true, Monsieur Poirot. It was the most awful hour of my life. I shall never forget it. But you are wonderful. I understand now----"

"What I meant when I told you that you could safely confess to Papa Poirot, eh? But you would not trust me."

"I see everything now," said Lawrence. "The drugged coco, taken on top of the poisoned coffee, amply accounts for the delay."

"Exactly. But was the coffee poisoned, or was it not? We come to a little difficulty here, since Mrs. Inglethorp never drank it."

"What?" The cry of surprise was universal.

"No. You will remember my speaking of a stain on the carpet in Mrs. Inglethorp's room? There were some peculiar points about that stain. It was still damp, it exhaled a strong odour of coffee, and imbedded in the nap of the carpet I found some little splinters of china. What had happened was plain to me, for not two minutes before I had placed my little case on the table near the window, and the table, tilting up, had deposited it upon the floor on precisely the identical spot. In exactly the same way, Mrs. Inglethorp had laid down her cup of coffee on reaching her room the night before, and the treacherous table had played her the same trick.

"What happened next is mere guess work on my part, but I should say that Mrs. Inglethorp picked up the broken cup and placed it on the table by the bed. Feeling in need of a stimulant of some kind, she heated up her coco, and drank it off then and there. Now we are faced with a new problem. We know the coco contained no strychnine. The coffee was never drunk. Yet the strychnine must have been administered between seven and nine o'clock that evening. What third medium was there--a medium so suitable for disguising the taste of strychnine that it is extraordinary no one has thought of it?" Poirot looked round the room, and then answered himself impressively. "Her medicine!"

"Do you mean that the murderer introduced the strychnine into her tonic?" I cried.

"There was no need to introduce it. It was already there--in the mixture. The strychnine that killed Mrs. Inglethorp was the identical strychnine prescribed by Dr. Wilkins. To make that clear to you, I will read you an extract from a book on dispensing which I found in the Dispensary of the Red Cross Hospital at Tadminster:

"'The following prescription has become famous in text books: Strychninae Sulph . . . . . . gr.I Potass Bromide . . . . . . . 3vi Aqua ad . . . . . . . . . . . 3viii Fiat Mistura

This solution deposits in a few hours the greater part of the strychnine salt as an insoluble bromide in transparent crystals. A lady in England lost her life by taking a similar mixture: the precipitated strychnine collected at the bottom, and in taking the last dose she swallowed nearly all of it!"

"Now there was, of course, no bromide in Dr. Wilkins' prescription, but you will remember that I mentioned an empty box of bromide powders. One or two of those powders introduced into the full bottle of medicine would effectually precipitate the strychnine, as the book describes, and cause it to be taken in the last dose. You will learn later that the person who usually poured out Mrs. Inglethorp's medicine was always extremely careful not to shake the bottle, but to leave the sediment at the bottom of it undisturbed.

"Throughout the case, there have been evidences that the tragedy was intended to take place on Monday evening. On that day, Mrs. Inglethorp's bell wire was neatly cut, and on Monday evening Mademoiselle Cynthia was spending the night with friends, so that Mrs. Inglethorp would have been quite alone in the right wing, completely shut off from help of any kind, and would have died, in all probability, before medical aid could have been summoned. But in her hurry to be in time for the village entertainment Mrs. Inglethorp forgot to take her medicine, and the next day she lunched away from home, so that the last--and fatal--dose was actually taken twenty-four hours later than had been anticipated by the murderer; and it is owing to that delay that the final proof--the last link of the chain--is now in my hands."

Amid breathless excitement, he held out three thin strips of paper.

"A letter in the murderer's own hand-writing, mes amis! Had it been a little clearer in its terms, it is possible that Mrs. Inglethorp, warned in time, would have escaped. As it was, she realized her danger, but not the manner of it."

In the deathly silence, Poirot pieced together the slips of paper and, clearing his throat, read:

"'Dearest Evelyn:

'You will be anxious at hearing nothing. It is all right--only it will be to-night instead of last night. You understand. There's a good time coming once the old woman is dead and out of the way. No one can possibly bring home the crime to me. That idea of yours about the bromides was a stroke of genius! But we must be very circumspect. A false step----'

"Here, my friends, the letter breaks off. Doubtless the writer was interrupted; but there can be no question as to his identity. We all know this hand-writing and----"

A howl that was almost a scream broke the silence.

"You devil! How did you get it?"

A chair was overturned. Poirot skipped nimbly aside. A quick movement on his part, and his assailant fell with a crash.

"Messieurs, mesdames," said Poirot, with a flourish, "let me introduce you to the murderer, Mr. Alfred Inglethorp!"

波洛的突然离去大大地引起了我们大家的好奇心。星期天早上过去了，他仍然没有出现。可是到三点左右，外面一声响亮、拖长的汽车喇叭声把我们都驱赶到窗口，只见波洛在贾普和萨默悔的陪同下，从一辆汽车里钻了出来。这小个子变了。他流露出一股可笑的自鸣得意的神情。他用过分的尊敬向玛丽·卡文迪什鞠了一个躬。

“大太，你允许我在客厅里开个小会吗？每个人都得出席。”

玛丽苦笑了一下。

“你知道，波洛先生，你有权安排一切。”

“你真是太温厚了，太太。”

波洛依然满脸笑容，把我们大家都集合到客厅里，他一面安排，一面往前搬着椅子。

“霍华德小姐——到了。辛西娅小姐。劳伦斯先生。诚实的多卡斯。还有安妮。好！我们的会还得延迟一会儿开始，等英格里桑先生来。我已经给他送去一个条子了。

霍华德小姐立即从座位上站了起来。

“要是那家伙进这屋里来，我马上离开这儿！”

“别这样，别这样！”波洛走到她跟前，低声请求说。

霍华德小姐终于答应，坐回到自己的椅子上。过了一会，英格里桑先生走进了客厅。

等人一到齐，波洛就从坐位上站了起来，摆出一个受欢迎的演说家的架势，向他的听众有礼貌地鞠了一个躬。

“先生们，女士们，正如你们诸位所知道的，我是受约翰·卡文迪什先生之约来调查此案的。我当时立即检查了死者的卧室，那间卧室根据医生们的建议，早已上了锁，因而它完全确切地保持着发生惨案时的情况。我在检查中发现：首先是一点绿色的布片；其次是，在窗口附近的地毯上有一片污迹，还是潮湿的；第三是，一只装溴化剂药粉的空盒子。

“先说这点绿色的布片，我发现，它钩在那间卧室和隔壁辛西娅小姐住的房间相通的那扇门的插销上。我曾经把这点布碎交给警方作过检查，他们认为这不很重要，但是他们认出了这是什么——这是一点从绿色务农臂章上撕下的布片。”

人们有点骚动起来了。

“目前，在斯泰尔斯只有一个人是务农的——就是卡文迪什太太。因此，一定是卡文迪什太太经由和辛西娅小姐房间相通的这道门进入过死看的房间。

“可是那道门是在里面闩上的呀！”我叫了起来。

“我去检查那房间时，是这样。但是，最初，这情况我们只是听她说的，因为去试看那道特别的门以及报告它闩住的都是她。在后来的混乱情况下，她是有足够的机会再把门闩上的。我早就找到一个机会检验过我的推测。首先，布片和卡文迪什太太臂章上一个扯破的小洞完全吻合。而且在验尸审讯时，卡文迪什太太还曾公开宣称，从自己的房里听到了床边那张桌子翻倒的声音。我也早已测验过她的这种说法，我要我的朋友哈斯丁站在房子的左侧，就在卡文迪什太太的门外。我自己和警方人员一起到了死者的房间，在那儿我表面上显得偶然地弄翻了谈论到的那张桌子，可是我发现，正如我所料想的那样，哈斯丁先生什么声音也没有听到。这使我更加相信，她公开宣称的惨案发生时她正在自己房里穿衣服，说的并不是真话。事实上，我确信，在响起报警的铃声时，卡文迪什太太并不是在自己的房里，而实际上是在死看的房中。”

我朝玛丽迅速地瞥了一眼。她的脸色非常苍白，但仍在微笑。

“我来继续说清这个假设的理由。卡文迪什太太在自己的婆婆的房中。我们可以说，她正在寻找什么东西，而且没找到。突然，英格里桑太太醒了过来，她以为毛病发作而感到一阵惊慌，猛地伸出手去，结果推翻了床头桌，接着不顾一切地拉响了电铃。卡文迪什太太大吃一惊，失手跌落了拿着的蜡烛，把浊油撒到了地毯上。她拾起蜡烛，飞快地退进辛西娅小姐的房间，关上了身后的门。她急匆匆地奔出房间来到过道里，因为不应当让佣人们发现她在这儿。但是已经太晚了！连接两侧的长廊那边已经传来脚步声。她该怎么办？她迅速一想，急忙退回到年轻姑娘的房间，并且动手把她摇醒。仓促地被唤醒的一家人聚集在过道里。他们都忙着猛敲英格里桑太太的房门，没有想到卡文迪什太太没有和其它人一起来，可是——这值得注意——我可以查明没有一个人看到她从另一侧过来。”他注视着玛丽·卡文迪什。“我说得对吗，太太？”

她点点头。

“一点没错，先生。你知道，要是我想到泄露这些事实会使我的丈夫有点好处的话，我早就这样做了。但是我觉得这并不关系到他的有罪或者无辜的问题。”

“在某种意义上说，这是正确的，太太。但是这能澄清我脑子里的许多错觉，现在让我来坦率他说一说那些真正有意义的事实吧。”

“遗嘱！”劳伦斯叫了起来。“那未它是你，玛丽，是谁烧毁那遗嘱的？”

她摇摇头，波洛也摇摇头。

“不，”他平静地说。“只有一个人有可能烧毁那遗嘱——就是英格里桑太太本人！”

“不可能！”我惊叫起来。“那是她当天下午刚写成的呀！”

“然而，我的朋友，这确实是英格里桑太太。因为，你没有其它的方法可以解释这样一个事实：在今年最热的日子里的一天，英格里桑太太竟然吩咐在她的房间里生火。”

我喘了一口气。我们真是傻瓜，从来都没有想到生火这多不合理！波洛继续说：

“那天的温度，先生们，在荫处为华氏80度，而英格里桑太太还吩咐生火！这为什么？因为她想要烧掉什么东西，不可能想到别的。你总还记得，由于在斯泰尔斯实行战时经济，连一张废纸也不让扔掉，因此像一份遗嘱这么厚的一份文件也不能烧掉。在我听到说在英格里桑太太房里生火的时候，我就匆匆武断地下了结论，这一定是要烧毁什么重要文件——可能是一份遗嘱。因此，在壁炉里发现烧焦的碎片并没有使我感到惊奇。当然，当时我不知道，我们讲到的这份遗嘱是这天下午刚立的，而且我得承认，当我听到这一事实后，我曾误入严重的歧途，我得出结论，认为英格里桑太太烧毁她的遗嘱的决定是由于当天下午发生争吵引起的直接结果，因此这次争吵系发生在立遗嘱之后，而不是立遗嘱之前。

“在这点上，正如我们所知道的，我搞错了，我被迫放弃了这个想法。我以一个新的观点来对待这个问题。哦，在四点钟时，多卡斯偶然听到她的女主人生气地说：‘你不要以为我怕公开出去，或者是夫妻间的反目能吓住我。’我对此作了推测，而且我的推测是正确的，这些话并不是对她的丈夫，而是对约翰·卡文迪什说的。五点钟时，即一小时之后，她说了几乎是同样的话，但是出发点不同。她对多卡斯承认，‘我不知道该怎么办；夫妻间的反目是一件可怕的事情。’四点钟时，她在生气，可本人完全是个女主人的样子。五点钟时，她已极度悲伤，说的话使人大为震惊。

“从心理学的角度来着这件事情，我得出一个结论，我认为这个结论是正确的。她第二次说的‘反目’不同于第一次——这是关于她自己的！

“让我们重新再来设想一下。四点钟时，英格里桑太太是和她的儿子争吵，威胁说要向她的妻子告发他——顺便说一句，他的妻子已碰巧听到了这次谈话的大部分。四点三十分时，英格里桑太太由于有了一次关于遗嘱的有效性问题的淡话之故，立了一份有利于他丈夫的遗嘱，这就是两个花匠连署的一份。五点钟时，多卡斯发现她的女主人的情绪相当激动不安，她手中拿着一张纸——多卡斯认为‘一封信’——这时她吩咐在她的房里生上火，有可能在当时，就是在四点三十分到五点之间，发生了什么事情，引起了她感情上非常剧烈的变化，因为这时她急干要烧毁这份遗嘱翼就象她在这以前，急于要立它一样。那么这是什么事情呢？

“就我们所知，在这半小时内，她完全是独自一人。没有一个人进来或者离开过那间闺房。那末是什么引起这一思想感情上的突变呢？”

“只能有一种推测，可是我相信我的推测是正确的。英格里桑太太的写字台里没有邮票。这我们知道，因为后来她曾要多卡斯给她拿一些来。而在那个房间的对角，放着她丈夫的写字台——是锁着的。她因为急于要找到几张邮票，于是，根据我的推论，她试图用自己的钥匙打开那张写字台。据我所知，其中有一只钥匙是配得上的。因此，她打开了写字台，而在寻找邮票的过程中，她偶然发现了一件别的东西——就是多卡斯看到她拿在手中的那张纸，这张东西无疑是决不能让英格里桑太太看到的。另一方面，卡文迪什太太却认为，她的婆婆如此紧紧地握着的这张纸是她自己的丈夫与人私通的书面证据。她要求英格里桑太太把这给她，她却要她放心，说是确实什么事情都没有发生。卡文迪什太太不相信她。她认为英格里桑太太在包庇自己的儿子。而卡文迪什太太是个非常果敢的女人，在她那谨慎自制的面纱后面，有的是对她丈夫的狂烈的妒忌。她决心要不惜一切代价来取得那份材料，而且在这种决心下有个机会帮助了她。她碰巧拾到英格里桑太太那大早上丢失的公文箱钥匙。她知道，她婆婆总是把重要的文件放在这只特殊的箱里的。

“因此，卡文迪什太太制订了自己的计划，就象只有一个因妒忌铤而走险的女人才会做出来的那样。傍晚的某个时候，她拉开了通往辛西娅小姐房间的那个门的插销。可能她还在折叶上点了油，因为我发现当我该着开门时，它一点声音也没有。她把她的计划拖延到那天凌晨，以便比较安全，因为在那个时候佣人们习惯干听到她在房间附近走动的声音。她穿好她的全套田间劳动服，悄俏地通过辛西娅小姐的房间，走进英格里桑太太的房间。”

他停顿了一下，辛西娅打断了他的话：

“可是，要是有人经过我的房间，我本当惊醒过来的呀？”

“要是你被麻醉了，你就醒不过来了，小姐。”

“麻醉？”

“是呀！”

“你们总还记得，”——他又对我们大家说——“一直都那么乱哄哄，可隔壁的辛西娅小姐却睡得那么沉。这有两种可能。不是她装睡——我不相信这一点——就是被某种人为的方法搞昏迷了。”

“脑子里带着后一种想法，我非常仔细地检查了全部咖啡杯，我记得前一天晚上拿咖啡给辛西娅小姐的是卡文迪什太太。我从每一只杯子里都取了试样，对它们进行了分析——由于没有结果，我又仔细地计算杯子，万一有一只已经拿走了呢。六个人喝过咖啡，六只杯子都在。我不得不承认自己错了。

“可是后来，我发现我犯了极为严重的粗枝大叶的错误。喝过咖啡的是七个人。而不是六个人，因为那天傍晚鲍斯坦医生也在那儿。这改变了整个事情的面貌，因为现在有一只杯子不见了。佣人们并没有引起注意，女佣人安妮端来了咖啡，拿进来七只杯子，她不知道英格里桑先生一直都没有喝，而第二天早上收杯子的多卡斯，象往常一样只找到六只——或者严格地说她只见到五只，这第六只就是发现打碎在英格里桑太太房里的一只。

“我确信不见的这只就是辛西娅小姐的那只。我之相信这一事实还有一个附带的理由，所有杯子里发现都放过糖，而辛西娅小姐是从来不在自己的咖啡里放糖的。我的注意力被安妮说的她每晚要送到英格里桑太太房里去的可可的托盘里发现一些“盐”的事吸引住了。因此我采了一点那可可的试样，把它送去作了分析。”

“可是鲍斯坦医生已经搞过了，”劳伦斯迅速地说。

“不完全如此。他只要求分析人员报告是否有士的宁。而不象我一样，要求化验是否有麻醉剂。”

“麻醉剂？”

“是的。这是分析人员的报告。卡文迪什太太给英格里桑太太和辛西娅小姐两人放了一种安全而有效的麻醉剂。这样她才有可能有一个‘作案”的时间！当她的婆婆突然死去，而且一听到‘毒药’这个字后，她的感觉是可以想象的！她相信，她所放的安眠药是完全无害的，但是，无疑，在那骇人的刹那间，她一定是害怕别人把英格里桑太太的死归罪到她头上了。她显得惊慌失措，在这种影响下，她匆匆跑到楼下，迅速把辛西娅小姐喝过的那只咖啡杯连同茶托一起扔进了一只黄铜大花瓶，后来它就是被劳伦斯先生在那里面找到的。而那留下来的可可，她碰也没敢去碰。看着她的眼睛太多了。当提到士的宁，而且她发现这整个惨案并非她所造成之后，她的宽慰是可以猜测到的。

“现在我们可以说明士的宁中毒的症状这么久才出现的原因了。麻醉剂和士的宁一起服下，使毒药的作用延缓了好几个小时。”

波洛停了一下。玛丽朝他着着，她的脸上渐渐有了血色。

“你说的全部是事实，波洛先生，这是我一生中最最庄严的时刻。我将永远不会忘记它。可是，你真是太好了。我现在知道——”

“我告诉过你，你向波洛神父忏悔错不了，我说的是什么意思，呢？可是你不信任我。”

“现在我一切都明白了，”劳伦斯说。“有麻醉剂的可可，加到了有毒药的咖啡上面，这就造成毒性发作延缓的原因。”

“一点不错。可是，咖啡是有毒的，还是没有毒的呢？这儿我们碰到了一点困难，因为英格里桑太太一直就没有喝咖啡。”

“什么？”大家都惊叫起来。

“没有喝。你们还记得我说的英格里桑太太房里地毯上的污迹吗？有关那污迹，有一些特点，它还是潮湿的，散发出强烈的咖啡味，而且渗进了地毯的绒毛，我还发现了一些很小的磁器碎未。发生的事情对我来说是一清二楚的。我曾把我的小公文箱放在靠窗的那张桌子上，可是桌子突然一边向上翘了起来，把它摔落到地板上，恰恰也落在了同一个地方。正是如此，头一天晚上，英格里桑太太把那杯拿到房里来的咖啡放了上去，而那张不牢靠的桌子也是这么捉弄了她一下。

“以后发生的情况，就我而言，仅仅是一种推论而已，但是我应当说，之后英格里桑太太拾起了打破的杯子，把它放到了床边的桌子上。她感到需要喝点兴奋的东西，于是就热了可可，当时就喝下去了。现在，我们面临了一个新的问题。我们知道，可可里不含士的宁，咖啡她又根本没有喝，而且士的宁一定是在傍晚七点到九点之间这段时间放的。这第三种媒介物是什么呢——一种能如此适合地掩盖掉士的宁的味道，以致奇怪地没有一个人想到它的东西？”波洛朝房间里环顾了一周，而后令人难忘地自己作了回答。“她的补药！”

“你的意思是凶手把士的宁放进了她的补药？”我大声问道。

“不需要放。它已经在里面了——在混合剂里。杀害英格里桑太太的土的宁是威尔金斯医生处方上开的同一种士的宁。为了使诸位清楚起见，我要给诸位念一念从一本药物配方书上抄下的一段摘录，这本书是我在塔明斯特红十字医院的药房里发现的：

“‘下述配方在教科书上已出名：

士的宁盐…………gr.1溴化钾……………3vi水…………………3viii混合

此溶液数小时后能使大部分士的宁盐沉淀为一种难以溶解的成透明晶体状溴化物。一英国女士因服用一种类似的混合剂丧生，因沉淀之士的宁均聚集在瓶底，而在服用最后一剂时，她近乎服下全部士的宁！’”

“当然，在威尔金斯医生的处方中并没有这种溴化物，但是诸位一定还记得我曾提到过一只溴化剂药粉的空盒子。放一、两包这种药粉到盛满的补药瓶里，就能使士的宁有效地沉淀，而象书上说的那样，使之服下那最后一剂。诸位以后一定会听到，这个惯常为英格里桑太太倒药的人，一直都非常当心，不去摇动瓶子，而在瓶底留下的沉淀物也就安然不动。”

“总之，有许多迹象表明惨案本当在星期一晚上发生。那一天，英格里桑太太的叫人铃的电线被整整齐齐地割断，当天晚上，辛西娅小姐又在朋友家过夜，因此在右侧屋只有英格里桑太太独自一人，这样就完全断绝了任何救助，而使她多半在请医生急救之前就死去。但是，那天晚上由于英格里桑太太急急忙忙地要赶去参加村子里的文娱晚会，她忘掉了服药，第二天，她又没有在家吃中饭，因此那最后——致命的——一剂药，实际上也就比凶手预期的迟服了二十四小时；正由于这一延迟，这决定性的证据——这根链条中的最后一环——现在落到了我的手中。”

在众人屏息的激动之中，他掏出了三张薄薄的纸条。

“一封凶手的亲笔信，朋友们！它在措词方面若更为清楚一点，要是及时得到警告，英格里桑太太是有可能得以免于被害的。其实，她已意识到自己处境的危险，但是她不知道杀害她的方法。”

在死一般的寂静中，波洛把几张纸条拼在一起，清了清嗓子，念道：

“‘最亲爱的伊夫琳：

你一定为听不到消息在着急吧。一切顺利

——只是它将在今天晚上而不是昨天晚上。你是

能理解的。等老太婆一死，处理掉，好日子就来

了。没有一个人能确实证明是我犯的罪。你的那

个有关溴化物的主意，真是天才的一着！不过我

们还得十分谨慎小心。走错一步——’

“朋友们，信到此为止。毫无疑问，笔者被打断了；但是，有关他的身分，已经不成问题。我们大家都知道，这手迹和——”

一声近乎尖叫的嚎吼打破了寂静。

“你混蛋！你怎么搞到它的？”

一张椅子被推翻了。波洛轻捷地跳到一旁。他飞快一个动作，攻击他的人就砰地一声跌倒在地。

“先生们，女士们，”波洛带着一种戏剧性的动作说。“请允许我向诸位介绍这位凶手——阿弗雷德·英格里桑先生！”

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