Japp and I agreed that that could be done easily enough - so long as no suspicion of foul play had arisen.
There was the particular coloring of the silk which I had no doubt was deliberately substituted for the original cerise so as to simulate the appearance of a wasp.
"Our murderer, then, approaches the victim's table, inserts the thorn and releases the wasp!
The poison is so powerful that death would occurr almost immediately.
If Giselle cried out, it would probably not be heard, owing to the noise of the plane.
If it was just noticed, well, there was a wasp buzzing about to explain the cry. The poor woman had been stung.
"That, as I say, was Plan No. 1.
But supposing that, as actually happened, the poisoned thorn was discovered before the murderer could retrieve it.
In that case, the fat is in the fire. The theory of natural death is impossible.
Instead of getting rid of the blowpipe through the window, it is put in a place where it is bound to be discovered when the plane is searched.
And at once it will be assumed that the blowpipe was the instrument of the crime. The proper atmosphere of distance will be created, and when the blowpipe is traced it will focus suspicion in a definite and prearranged direction.
"I had now my theory of the crime, and I had three suspects, with a barely possible fourth - M. Jean Dupont who had outlined the Death-by-a-wasp-sting theory, and who was sitting on the gangway so near Giselle that he might just possibly have moved from his seat without being noticed.
On the other hand, I did not really think he would have dared to take such a risk.
"I concentrated on the problem of the wasp.
If the murderer had brought the wasp onto the plane and released it at the psychological moment, he must have had something in the nature of a small box in which to keep it.
"Hence my interest in the contents of the passengers pockets and hand luggage.
"And here I came up against a totally unexpected development.
I found what I was looking for - but, as it seemed to me, on the wrong person.
There was an empty small-sized Bryant & May's match box in Mr Norman Gale's pocket.
But by everybody's evidence, Mr Gale had never passed down the gangway of the car.
He had only visited the wash-room compartment and returned to his own seat.
"Nevertheless, although it seems impossible, there was a method by which Mr Gale could have committed the crime - as the contents of his attache case showed."
"My attache case?" said Norman Gale. He looked amused and puzzled. "Why, I don't even remember now what was in it."
Poirot smiled at him amiably.
"Wait a little minute. I will come to that.
I am telling you my first ideas.
"To proceed, I had four persons who could have done the crime - from the point of view of possibility. The two stewards, Clancy and Gale.
"I now looked at the case from the opposite angle - that of motive; if a motive were to coincide with a possibility - well, I had my murderer!
But alas, I could find nothing of the kind.
My friend Japp has accused me of liking to make things difficult.
On the contrary, I approached this question of motive with all the simplicity in the world.
To whose benefit would it be if Madame Giselle were removed?
Clearly, to her unknown daughter's benefit, since that unknown daughter would inherit a fortune.
There were also certain persons who were in Madame Giselle's power - or shall we say, who might be in Giselle's power for aught we knew? That, then, was a task of elimination.
Of the passengers in the plane I could only be certain of one who was undoubtedly mixed up with Giselle. That one was Lady Horbury.
"In Lady Horbury's case the motive was clear.
She had visited Giselle at her house in Paris the night before.
She was desperate and she had a friend, a young actor, who might easily have impersonated the American who bought the blowpipe, and might also have bribed the clerk in Universal Air Lines to insure that Giselle traveled by the twelve o'clock service.
"I had, as it were, a problem in two halves. I did not see how it was possible for Lady Horbury to commit the crime. And I could not see for what motive the stewards, Mr Clancy or Mr Gale should want to commit it.
"Always, in the back of my mind, I considered the problem of Giselle's unknown daughter and heiress.
Were any of my four suspects married, and if so, could one of the wives be this Anne Morisot?
If her father was English, the girl might have been brought up in England.
Mitchell's wife I soon dismissed - she was of good old Dorset country stock.
Davis was courting a girl whose father and mother were alive.
Mr Clancy was not married.
Mr Gale was obviously head over ears in love with Miss Jane Grey.
"I may say that I investigated the antecedents of Miss Grey very carefully, having learned from her in casual conversation that she had been brought up in an orphanage near Dublin.
But I soon satisfied myself that Miss Grey was not Madame Giselle's daughter.
"I made out a table of results.
The stewards had neither gained nor lost by Madame Giselle's death, except that Mitchell was obviously suffering from shock.