“why did you measure that overcoat?” i asked, with some curiosity, as we walked down the hot white road at a leisurely pace.

“parbleu! to see how long it was,” replied my friend imperturbably.

i was vexed. poirot’s incurable habit of making a mystery out of nothing never failed to irritate me. i relapsed into silence, and followed a train of thought of my own. although i had not noticed them specially at the time, certain words mrs. renauld had addressed to her son now recurred to me, fraught with a new significance. “so you did not sail?” she had said, and then had added: “after all, it does not matter—now.”

what had she meant by that? the words were enigmatical—significant. was it possible that she knew more than we supposed? she had denied all knowledge of the mysterious mission with which her husband was to have entrusted his son. but was she really less ignorant than she pretended? could she enlighten us if she chose, and was her silence part of a carefully thought out and preconceived plan?

the more i thought about it, the more i was convinced that i was right. mrs. renauld knew more than she chose to tell. in her surprise at seeing her son, she had momentarily betrayed herself. i felt convinced that she knew, if not the assassins, at least the motive for the assassination. but some very powerful considerations must keep her silent.

“you think profoundly, my friend,” remarked poirot, breaking in upon my reflections. “what is it that intrigues you so?”

i told him, sure of my ground, though feeling expectant that he would ridicule my suspicions. but to my surprise he nodded thoughtfully.

“you are quite right, hastings. from the beginning i have been sure that she was keeping something back. at first i suspected her, if not of inspiring, at least of conniving at the crime.”

“you suspected her?” i cried.

“but certainly! she benefits enormously—in fact, by this new will, she is the only person to benefit. so, from the start, she was singled out for attention. you may have noticed that i took an early opportunity of examining her wrists. i wished to see whether there was any possibility that she had gagged and bound herself. eh bien, i saw at once that there was no fake, the cords had actually been drawn so tight as to cut into the flesh. that ruled out the possibility of her having committed the crime single-handed. but it was still possible for her to have connived at it, or to have been the instigator with an accomplice. moreover, the story, as she told it, was singularly familiar to me—the masked men that she could not recognize, the mention of ‘the secret’—i had heard, or read, all these things before. another little detail confirmed my belief that she was not speaking the truth. the wrist watch, hastings, the wrist watch!”

again that wrist watch! poirot was eyeing me curiously.

“you see, mon ami? you comprehend?”

“no,” i replied with some ill humour. “i neither see nor comprehend. you make all these confounded mysteries, and it’s useless asking you to explain. you always like keeping everything up your sleeve to the last minute.”

“do not enrage yourself, my friend,” said poirot with a smile. “i will explain if you wish. but not a word to giraud, c’est entendu? he treats me as an old one of no importance! we shall see! in common fairness i gave him a hint. if he does not choose to act upon it, that is his own look out.”

i assured poirot that he could rely upon my discretion.

“c’est bien! let us then employ our little grey cells. tell me, my friend, at what time, according to you, did the tragedy take place?”

“why, at two o’clock or thereabouts,” i said, astonished. “you remember, mrs. renauld told us that she heard the clock strike while the men were in the room.”

“exactly, and on the strength of that, you, the examining magistrate, bex, and every one else, accept the time without further question. but i, hercule poirot, say that madame renauld lied. the crime took place at least two hours earlier.”

“but the doctors—”

“they declared, after examination of the body, that death had taken place between ten and seven hours previously. mon ami, for some reason, it was imperative that the crime should seem to have taken place later than it actually did. you have read of a smashed watch or clock recording the exact hour of a crime? so that the time should not rest on mrs. renauld’s testimony alone, some one moved on the hands of that wrist watch to two o’clock, and then dashed it violently to the ground. but, as is often the case, they defeated their own object. the glass was smashed, but the mechanism of the watch was uninjured. it was a most disastrous manoeuvre on their part, for it at once drew my attention to two points—first, that madame renauld was lying: secondly, that there must be some vital reason for the postponement of the time.”

“but what reason could there be?”

“ah, that is the question! there we have the whole mystery. as yet, i cannot explain it. there is only one idea that presents itself to me as having a possible connection.”

“and that is?”

“the last train left merlinville at seventeen minutes past twelve.”

i followed it out slowly.

“so that, the crime apparently taking place some two hours later, any one leaving by that train would have an unimpeachable alibi!”

“perfect, hastings! you have it!”

i sprang up.

“but we must inquire at the station. surely they cannot have failed to notice two foreigners who left by that train! we must go there at once!”

“you think so, hastings?”

“of course. let us go there now.”

poirot restrained my ardour with a light touch upon the arm.

“go by all means if you wish, mon ami—but if you go, i should not ask for particulars of two foreigners.”

i stared, and he said rather impatiently:

“là, là, you do not believe all that rigmarole, do you? the masked men and all the rest of cette histoire-là!”

his words took me so much aback that i hardly knew how to respond. he went on serenely:

“you heard me say to giraud, did you not, that all the details of this crime were familiar to me? eh bien, that presupposes one of two things, either the brain that planned the first crime also planned this one, or else an account read of a cause célèbre unconsciously remained in our assassin’s memory and prompted the details. i shall be able to pronounce definitely on that after—” he broke off.

i was revolving sundry matters in my mind.

“but mr. renauld’s letter? it distinctly mentions a secret and santiago?”

“undoubtedly there was a secret in m. renauld’s life—there can be no doubt of that. on the other hand, the word santiago, to my mind, is a red herring, dragged continually across the track to put us off the scent. it is possible that it was used in the same way on m. renauld, to keep him from directing his suspicions into a quarter nearer at hand. oh, be assured, hastings, the danger that threatened him was not in santiago, it was near at hand, in france.”

he spoke so gravely, and with such assurance, that i could not fail to be convinced. but i essayed one final objection:

“and the match and cigarette end found near the body? what of them.”

a light of pure enjoyment lit up poirot’s face.

“planted! deliberately planted there for giraud or one of his tribe to find! ah, he is smart, giraud, he can do his tricks! so can a good retriever dog. he comes in so pleased with himself. for hours he has crawled on his stomach. ‘see what i have found,’ he says. and then again to me: ‘what do you see here?’ me, i answer, with profound and deep truth, ‘nothing.’ and giraud, the great giraud, he laughs, he thinks to himself, ‘oh, that he is imbecile, this old one!’ but we shall see. …”

but my mind had reverted to the main facts.

“then all this story of the masked men—?”

“is false.”

“what really happened?”

poirot shrugged his shoulders.

“one person could tell us—madame renauld. but she will not speak. threats and entreaties would not move her. a remarkable woman that, hastings. i recognized as soon as i saw her that i had to deal with a woman of unusual character. at first, as i told you, i was inclined to suspect her of being concerned in the crime. afterwards i altered my opinion.”

“what made you do that?”

“her spontaneous and genuine grief at the sight of her husband’s body. i could swear that the agony in that cry of hers was genuine.”

“yes,” i said thoughtfully, “one cannot mistake these things.”

“i beg your pardon, my friend—one can always be mistaken. regard a great actress, does not her acting of grief carry you away and impress you with its reality? no, however strong my own impression and belief, i needed other evidence before i allowed myself to be satisfied. the great criminal can be a great actor. i base my certainty in this case, not upon my own impression, but upon the undeniable fact that mrs. renauld actually fainted. i turned up her eyelids and felt her pulse. there was no deception—the swoon was genuine. therefore i was satisfied that her anguish was real and not assumed. besides, a small additional point not without interest, it was unnecessary for mrs. renauld to exhibit unrestrained grief. she had had one paroxysm on learning of her husband’s death, and there would be no need for her to simulate another such a violent one on beholding his body. no, mrs. renauld was not her husband’s murderess. but why has she lied? she lied about the wrist watch, she lied about the masked men—she lied about a third thing. tell me, hastings, what is your explanation of the open door?”

“well,” i said, rather embarrassed, “i suppose it was an oversight. they forgot to shut it.”

poirot shook his head, and sighed.

“that is the explanation of giraud. it does not satisfy me. there is a meaning behind that open door which for a moment i cannot fathom.”

“i have an idea,” i cried suddenly.

“a la bonne heure! let us hear it.”

“listen. we are agreed that mrs. renauld’s story is a fabrication. is it not possible, then, that mr. renauld left the house to keep an appointment—possibly with the murderer—leaving the front door open for his return. but he did not return, and the next morning he is found, stabbed in the back.”

“an admirable theory, hastings, but for two facts which you have characteristically overlooked. in the first place, who gagged and bound madame renauld? and why on earth should they return to the house to do so? in the second place, no man on earth would go out to keep an appointment wearing his underclothes and an overcoat. there are circumstances in which a man might wear pajamas and an overcoat—but the other, never!”

“true,” i said, rather crest-fallen.

“no,” continued poirot, “we must look elsewhere for a solution of the open door mystery. one thing i am fairly sure of—they did not leave through the door. they left by the window.”

“what?”

“precisely.”

“but there were no footmarks in the flower bed underneath.”

“no—and there ought to have been. listen, hastings. the gardener, auguste, as you heard him say, planted both those beds the preceding afternoon. in the one there are plentiful impressions of his big hobnailed boots—in the other, none! you see? some one had passed that way, some one who, to obliterate their footprints, smoothed over the surface of the bed with a rake.”

“where did they get a rake?”

“where they got the spade and the gardening gloves,” said poirot impatiently. “there is no difficulty about that.”

“what makes you think that they left that way, though? surely it is more probable that they entered by the window, and left by the door.”

“that is possible of course. yet i have a strong idea that they left by the window.”

“i think you are wrong.”

“perhaps, mon ami.”

i mused, thinking over the new field of conjecture that poirot’s deductions had opened up to me. i recalled my wonder at his cryptic allusions to the flower bed and the wrist watch. his remarks had seemed so meaningless at the moment and now, for the first time, i realized how remarkably, from a few slight incidents, he had unravelled much of the mystery that surrounded the case. i paid a belated homage to my friend. as though he read my thoughts, he nodded sagely.

“method, you comprehend! method! arrange your facts. arrange your ideas. and if some little fact will not fit in—do not reject it but consider it closely. though its significance escapes you, be sure that it is significant.”

“in the meantime,” i said, considering, “although we know a great deal more than we did, we are no nearer to solving the mystery of who killed mr. renauld.”

“no,” said poirot cheerfully. “in fact we are a great deal further off.”

the fact seemed to afford him such peculiar satisfaction that i gazed at him in wonder. he met my eye and smiled.

“but yes, it is better so. before, there was at all events a clear theory as to how and by whose hands he met his death. now that is all gone. we are in darkness. a hundred conflicting points confuse and worry us. that is well. that is excellent. out of confusion comes forth order. but if you find order to start with, if a crime seems simple and above-board, eh bien, méfiez vous! it is, how do you say it?—cooked! the great criminal is simple—but very few criminals are great. in trying to cover up their tracks, they invariably betray themselves. ah, mon ami, i would that some day i could meet a really great criminal—one who commits his crime, and then—does nothing! even i, hercule poirot, might fail to catch such a one.”

but i had not followed his words. a light had burst upon me.

“poirot! mrs. renauld! i see it now. she must be shielding somebody.”

from the quietness with which poirot received my remark, i could see that the idea had already occurred to him.

“yes,” he said thoughtfully. “shielding some one—or screening some one. one of the two.”

i saw very little difference between the two words, but i developed my theme with a good deal of earnestness. poirot maintained a strictly non-committal attitude, repeating:

“it may be—yes, it may be. but as yet i do not know! there is something very deep underneath all this. you will see. something very deep.”

then, as we entered our hotel, he enjoined silence on me with a gesture.