be surprised； but she would be quite unsuspicious。 Perhaps he draws her attention to something out the window； and as she turns to look he slips the cord round her neck … and the whole thing is over in a second or two。 The door of the partment is locked； and he and Ada Mason set to work。 They strip off the dead woman's outer clothes。 Mason and Knighton roll the body up in a rug and put it on the seat in the adjoining partment amongst the bags and suitcases。 Knighton drops off the train； taking the jewel…case containing the rubies with him。 Since the crime is not supposed to have been mitted until nearly twelve hours later he is perfectly safe； and his evidence and the supposed Mrs Kettering's words to the conductor will provide a perfect alibi for his acplice。
〃At the Gare de Lyon Ada Mason gets a dinner basket； and shutting herself into the toilet partment she quickly changes into her mistress's clothes； adjusts two false bunches of auburn curls； and generally makes up to resemble her as closely as possible。 When the conductor es to make up the bed； she tells him the prepared story about having left her maid behind in Paris； and whilst he is making up the berth； she stands looking out of the window； so that her back is towards the corridor and people passing along there。 That was a wise precaution； because； as we know； Miss Grey was one of those passing； and she among others； was willing to swear that Mrs Kettering was still alive at that hour。〃
〃Go on；〃 said Van Aldin。
〃Before getting to Lyons； Ada Mason arranged her mistress's body in the bunk； folded up the dead woman's clothes neatly on the end of it； and herself changed into a man's clothes and prepared to leave the train。 When Derek Kettering entered his wife's partment； and； as he thought； saw her asleep in her berth； the scene had been set； and Ada Mason was hidden in the next partment waiting for the moment to leave the train unobserved。 As soon as the conductor had swung himself down on to the platform at Lyons； she follows； slouching along as though just taking a breath of air。 At a moment when she is unobserved； she hurriedly crosses to the other platform； and takes the first train back to Paris and the Ritz Hotel。 Her name has been registered there as taking a room the night before by one of Knighton's female acplices。 She has nothing to do but wait there placidly for your arrival。 The jewels are not； and never have been； in her possession。 Kettering had them。 No suspicion attaches to him； and； as your secretary； he brings them to Nice without the least fear of discovery。 Their delivery there to Monsieur Papopolous is already arranged for and they are entrusted to Mason at the last moment to hand over to the Greek。 Altogether a very neatly planned coup； as one would expect from a master of the game such as the Marquis。〃
〃And you honestly mean that Richard Knighton is a well…known criminal； who has been at this business for years？〃
Poirot nodded。
〃One of the chief assets of the gentleman called the Marquis was his plausible； ingratiating manner。 You fell a victim to his charm； Monsieur Van Aldin； when you engaged him as a secretary on such a slight acquaintanceship？〃
〃I could have sworn that he never angled for the post；〃 cried the millionaire。
〃It was very astutely done … so astutely done that it deceived a man whose knowledge of other men is as great as yours is。〃
〃I looked up his antecedents too。 The fellow's record was excellent。〃
〃Yes； yes； that was part of the game。 As Richard Knighton his life reproach。 He was well…born； well…connected； did honourable service in the war； and seemed altogether above suspicion； but when I came to glean information about the mysterious Marquis； I found many points of similarity。 Knighton spoke French like a Frenchman； he had been in America； France； and England at much the same time as the Marquis was operating。 The Marquis was last heard of as engineering various jewel robberies in Switzerland； and it was in Switzerland that you had e across Major Knighton； and it was at precisely that time that the first rumours were going round of your being in treaty for the famous rubies。〃
〃But why murder？〃 murmured Van Aldin brokenly。 〃Surely a clever thief could have stolen the jewels without running his head into a noose。〃
Poirot shook his head。 〃This is not the first murder that lies to the Marquis's charge。 He is a killer by instinct； he believes； too； in leaving no evidence behind him。 Dead men and women tell no tales。
〃The Marquis had an intense passion for famous and historical jewels。 He laid his plans far beforehand by installing himself as your secretary and getting his acplice to obtain the situation of maid with your daughter； for whom he guessed the jewels were destined。 And； though this was his matured and carefully thought…out plan； he did not scruple to attempt a short…cut by hiring a couple of Apaches to waylay you in Paris on the night you bought the jewels。 That plan failed； which hardly surprised him； I think。 This plan was； so he thought； pletely safe。 No possible suspicion could attach to Richard Knighton。 But like all great men … and the Marquis was a great man … he had his weaknesses。 He fell genuinely in love with Miss Grey； and suspecting her liking for Derek Kettering； he could not resist the temptation to saddle him with the crime when the opportunity presented itself。 And now； Monsieur Van Aldin； I am going to tell you something very curious。 Miss Grey is not a fanciful woman by any means； yet she firmly believes that she felt your daughter's presence beside her one day in the Casino Gardens at Monte Carlo； just after she had been having a long talk with Knighton。 She was convinced； she says； that the dead woman was urgently trying to tell her something； and it suddenly came to her that what the dead woman was trying to say was that Knighton was her murderer！ The idea seemed so fantastic at the time that Miss Grey spoke of it to no one。 But she was so convinced of its truth that she acted on it … wild as it seemed。 She did not discourage Knighton's advances； and she pretended to him that she was convinced of Derek Kettering's guilt。〃
〃Extraordinary；〃 said Van Aldin。
〃Yes； it is very strange。 One cannot explain these things。 Oh； by the way； there is one little point that baffled me considerably。 Your secretary has a decided limp … the result of a wound that he received in the ost decidedly did not limp。 That was a stumbling…block。 But Miss Lenox Tamplin happened to mention one day that Knighton's limp had been a surprise to the surgeons who had been in charge of the case in her mother's hospital。 That suggested camouflage。 When I was in London I went to the surgeon in question； and I got several technical details from him which confirmed me in that belief。 I mentioned the name of that surgeon in Knighton's hearing the day before yesterday。 The natural thing would have been for Knighton to mention that he had been attended by him during the war； but he said nothing … and that little point； if nothing else； gave me the last final assurance that my theory of the crime was correct。 Miss Grey； too； provided me with a cutting； showing that there had been a robbery at Lady Tamplin's hospital during the time that Knighton had been there。 She realized that I was on the same track as herself when I wrote to her from the Ritz in Paris。
〃I had some trouble in my inquiries there； but I got what I wanted … evidence that Ada Mason arrived on the morning after the crime and not on the evening of the day before。〃
There was a long silence； then the millionaire stretched out a hand to Poirot across the table。
〃I guess you know what this means to me； Monsieur Poirot；〃 he said huskily。 〃I am sending you round a cheque in the morning； but no cheque in the world will express what I feel about what you have done for me。 You are the goods； Monsieur Poirot。 Every time； you are the goods。〃
Poirot rose to his feet； his chest swelled。
〃I am only Hercule Poirot；〃 he said modestly； 〃yet； as you say； in my own way I am a big man； even as you also are a big man。 I am glad and happy to have been of service to you。 Now I go to repair the damages caused by travel。 Alas！ my excellent Georges is not with me。〃
In the lounge of the hotel he encountered a friend … the venerable Monsieur Papopolous； his daughter Zia beside him。
〃I thought you had left Nice； Monsieur Poirot；〃 murmured the Greek as he took the detective's affectionately proffered hand。
〃Business pelled me to return； my dear Monsieur Papopolous。〃
〃Business？〃
〃Yes； business。 And talking of business； I hope your health is better； my dear friend？〃
〃Much better。 In fact； we are returning to Paris tomorrow。〃
〃I am enchanted to hear such good news。 You have not pletely ruined the Greek ex…Minister； I hope。〃
〃I？〃
〃I understand you sold him a very wonderful ruby which … strictly entre nous … is being worn by Mademoiselle Mirelle； the dancer？〃
〃Yes；〃 murmured Monsieur Papopolous； 〃yes； that is so。〃
〃A ruby not unlike the famous 'Heart of Fire'？〃
〃It has points of resemblance； certainly；〃 said the Greek casually。
〃You have a wonderful hand with jewels； Monsieur Papopolous。 I congratulate you。 Mademoiselle Zia； I am desolate that you are returning to Paris so speedily。 I had hoped to see some more of you now that my business is acplished。〃
〃Would one be indiscreet if one asked what that business was？〃 asked Monsieur Papopolous。
〃Not at all； not at all。 I have just succeeded in laying the Marquis by the heels。〃
A far…away look came over Monsieur Papopolous' noble countenance。
〃The Marquis？〃 he murmured； 〃now why does that seem familiar to me？ No … I cannot recall it。〃
〃You would not； I am sure；〃 said Poirot。 〃I refer to a very notable criminal and jewel robber。 He has just been arrested for the murder of the English lady； Madame Kettering。〃
〃Indeed？ How interesting these things are！〃
A polite exchange of farewells followed； and when Poirot was out of earshot。 Monsieur Papopolous turned to his daughter。
〃Zia；〃 he said； with feeling； 〃that man is the devil！〃
〃I like him。〃
〃I like him myself；〃 admitted Monsieur Papopolous。 〃But he is the devil； al