re。' I ask you； Monsieur Van Aldin； whether you would be glad or sorry if what I tell you should be the case？〃
Van Aldin stared at him。 〃Naturally I should be glad；〃 he said at last。 〃Is this an exercise in suppositions； Monsieur Poirot； or are there any facts behind it？〃
Poirot looked at the ceiling。
〃There is an off…chance；〃 he said quietly； 〃that it might be the te de la Roche after all。 At least I have succeeded in upsetting his alibi。〃
〃How did you manage that？〃
Poirot shrugged his shoulders modestly。
〃I have my own methods。 The exercise of a little tact； a little cleverness … and the thing is done。〃
〃But the rubies；〃 said Van Aldin； 〃these rubies that the Count had in his possession were false。〃
〃And clearly he would not have mitted the crime except for the rubies。 But you are overlooking one point； Monsieur Van Aldin。 Where the rubies were concerned； someone might have been before him。〃
〃But this is an entirely new theory；〃 cried Knighton。
〃Do you really believe all this rigmarole； Monsieur Poirot？〃 demanded the millionaire。
〃The thing is not proved；〃 said Poirot quietly。 〃It is as yet only a theory； but I tell you this； Monsieur Van Aldin； the facts are worth investigating。 You must e out with me to the south of France and go into the case on the spot。〃
〃You really think this is necessary … that I should go； I mean。〃
〃I thought it would be what you yourself would wish；〃 said Poirot。
There was a hint of reproach in his tone which was not lost upon the other。
〃Yes； yes； of course；〃 he said。 〃When do you wish to start； Monsieur Poirot？〃
〃You are very busy at present； sir；〃 murmured Knighton。
But the millionaire had now made up his mind； and he waved the other's objections aside。
〃I guess this business es first；〃 he said。 〃All right； Monsieur Poirot； tomorrow。 What train？〃
〃We will go； I think； by the Blue Train；〃 said Poirot； and he smiled。
Chapter 34
THE BLUE TRAIN AGAIN
'The millionaire's train；' as it is sometimes called； swung round a curve of line at what seemed a dangerous speed。 Van Aldin； Knighton and Poirot sat together in silence。
Knighton and Van Aldin had two partments connecting with each other； as Ruth Kettering and her maid had had on the fateful journey。 Poirot's own partment was further along the coach。
The journey was a painful one for Van Aldin； recalling as it did the most agonizing memories。 Poirot and Knighton conversed occasionally in low tones without disturbing him。
When； however； the train had pleted its slow journey round the ceinture and reached the Gare de Lyon； Poirot became suddenly galvanized into activity。 Van Aldin realized that part of his object in travelling by the train had been to attempt to reconstruct the crime。 Poirot himself acted every part。 He was in turn the maid； hurriedly shut into her own partment； Mrs Kettering； recognizing her husband with surprise and a trace of anxiety； and Derek Kettering discovering that his wife was travelling on the train。 He tested various possibilities； such as the best way for a person to conceal himself in the second partment。
Then suddenly an idea seemed to strike him。 He clutched at Van Aldin's arm。
〃Mon Dieu； but that is something I have not thought of！ We must break our journey in Paris。 Quick； quick； let us alight at once。〃
Seizing suitcases he hurried from the train。 Van Aldin and Knighton； bewildered but obedient； followed him。 Van Aldin having once formed his opinion of Poirot's ability was slow to part from it。 At the barrier they were held up。 Their tickets were in charge of the conductor of the train； a fact which all three of them had forgotten。
Poirot's explanations were rapid； fluent； and impassioned； but they produced no effect upon the stolid…faced official。
〃Let us get quit of this；〃 said Van Aldin abruptly。 〃I gather you are in a hurry； Monsieur Poirot。 For God's sake pay the fares from Calais and let us get right on with whatever you have got in your mind。〃
But Poirot's flood of language had suddenly stopped dead； and he had the appearance of a man turned to stone。 His arm still outflung in an impassioned gesture； remained there as though stricken with paralysis。
〃I have been an imbecile；〃 he said simply。 〃Ma foi； I lose my head nowadays。 Let us return and continue our journey quietly。 With reasonable luck the train will not have gone。〃
They were only just in time； the train moving off as Knighton； the last of the three； swung himself and his suitcase on board。
The conductor remonstrated with them feelingly； and assisted them to carry their luggage back to their partments。 Van Aldin said nothing； but he was clearly disgusted at Poirot's extraordinary conduct。
Alone with Knighton for a moment or two； he remarked：
〃This is a wild goose chase。 The man has lost his grip on things。 He has got brains up to a point； but any man who loses his head and scuttles round like a frightened rabbit is no earthly darned good。〃
Poirot came to them in a moment or two； full of abject apologies and clearly so crestfallen that harsh words would have been superfluous。
Van Aldin received his apologies gravely； but managed to restrain himself from making acid ments。
They had dinner on the train； and afterwards； somewhat to the surprise of the other two； Poirot suggested that they should all three sit up in Van Aldin's partment。
The millionaire looked at him curiously。
〃Is there anything that you are keeping back from us； Monsieur Poirot？〃
〃I？〃 Poirot opened his eyes in innocent surprise。 〃But what an idea。〃
Van Aldin did not answer； but he was not satisfied。 The conductor was told that he need not make up the beds。 Any surprise he might have felt was obliterated by the largeness of the tip which Van Aldin handed to him。 The three men sat in silence。 Poirot fidgeted and seemed restless。 Presently he turned to the secretary。
〃Major Knighton； is the door of your partment bolted？ The door into the corridor； I mean。〃
〃Yes； I bolted it myself just now。〃
〃Are you sure？〃 said Poirot。
〃I will go and make sure； if you like；〃 said Knighton smiling。
〃No； no； do not derange yourself。 I will see for myself。〃
He passed through the connecting door and returned in a second or two； nodding his head。
〃Yes； yes； it is as you said。 You must pardon an old man's fussy ways。〃
He closed the connecting door and resumed his place in the right…hand corner。
The hours passed。 The three men dozed fitfully； waking with unfortable starts。
Probably never before had three people booked berths on the most luxurious train available； then declined to avail themselves of the acmodation they had paid for。
Every now and then Poirot glanced at his watch； and then nodded his head and posed himself to slumber once more。 On one occasion he rose from his seat and opened the connecting door； peered sharply into the adjoining partment； and then returned to his seat； shaking his head。
〃What is the matter？〃 whispered Knighton。 〃You are expecting something to happen； aren't you？〃
〃I have the nerves；〃 confessed Poirot。 〃I am like the cat upon the hot tiles。 Every little noise it makes me jump。〃
Knighton yawned。
〃Of all the darned unfortable journeys；〃 he murmured。 〃I suppose you know what you are playing at； Monsieur Poirot。〃
He posed himself to sleep as best he could。 Both he and Van Aldin had succumbed to slumber； when Poirot； glancing for the fourteenth time at his watch； leant across and tapped the millionaire on the shoulder。
〃Eh？ What is it？〃
〃In five or ten minutes； Monsieur； we shall arrive at Lyons。〃
〃My God！〃 Van Aldin's face looked white and haggard in the dim light。 〃Then it must have been about this time that poor Ruth was killed。〃
He sat staring straight in front of him。 His lips twitched a little； his mind reverting back to the terrible tragedy that had saddened his life。
There was the usual long screaming sigh of the brake； and the train slackened speed and drew into Lyons。 Van Aldin let down the window and leant out。
〃If it wasn't Derek … if your new theory is correct； it is here that the man left the train？〃 he asked over his shoulder。
Rather to his surprise Poirot shook his head。
〃No；〃 he said thoughtfully； 〃no man left the train； but I think … yes； I think； a woman may have done so。〃
Knighton gave a gasp。
〃A woman？〃 demanded Van Aldin sharply。
〃Yes； a woman；〃 said Poirot； nodding his head。 〃You may not remember； Monsieur Van Aldin； but Miss Grey in her evidence mentioned that a youth in a cap and overcoat descended on to the platform ostensibly to stretch his legs。 Me； I think that that youth was most probably a woman。〃
〃But who was she？〃
Van Aldin's face expressed incredulity； but Poirot replied seriously and categorically。
〃Her name … or the name under which she was known； for many years … is Kitty Kidd； but you； Monsieur Van Aldin； knew her by another name … that of Ada Mason。〃
Knighton sprang to his feet。
〃What？〃 he cried。
Poirot swung round to him。
〃Ah！ … before I forget it。〃 He whipped something from a pocket and held it out。
〃Permit me to offer you a cigarette … out of your own cigarette…case。 It was careless of you to drop it when you boarded the train on the ceinture at Paris。〃
Knighton stood staring at him as though stupefied。 Then he made a movement； but Poirot flung up his hand in a warning gesture。
〃No； don't move；〃 he said in a silky voice； 〃the door into the next partment is open； and you are being covered from there this minute。 I unbolted the door into the corridor when we left Paris； and our friends the police were told to take their places there。 As I expect you know； the French police want you rather urgently； Major Knighton … or shall we say … Monsieur le Marquis？〃
Chapter 35
EXPLANATIONS
〃Explanations？〃
Poirot smiled。 He was sitting opposite the millionaire at a luncheon table in the latter's private suite at the Negresco。 Facing him was a relieved but very puzzled man。 Poirot leant back in his chair； lit one of his tiny cigarettes； and stared reflectively at the ceiling。
〃Yes； I will give you explanations。 It began with the one point that puzzled me。 You know what that point was？ The disfigured face。 It is not an unmon thing to find when investigating a crime and it rouses an immediate question； the question of identity。 That naturally was the first thing that occurred to me。 Was the dead woman really Mrs Kettering？ But that line led me nowhere； for Miss Grey's evidence was positive and very reliable； so I put that idea aside。 The dead woman was Ruth Kettering。〃
〃When did you first begin to suspect the maid？〃
〃Not for some time； but one peculiar little point drew my attention to her。 The cigarette…case found in the railway carriage and which she told us was one which Mrs Kettering had given to her husband。 Now that was； on the face of it； most improbable； seeing the terms that they were on。 It awakened a doubt in my mind as to the general veracity of Ada Mason's statements。 There was the rather suspicious fact to be taken into consideration； that she had only been with her mistress for two months。 Certainly it did not seem as if she could ha