Bouc. “You comprehend what I am about to ask of you. I know your powers. Take command of this investigation! No, no, do not refuse. See, to us it is serious-I speak for the Compagnie Internationale des Wagons Lits. By the time the Jugo-Slavian police arrive, how simple if we can present them with the solution! Otherwise delays, annoyances, a million and one inconveniences. Perhaps, who knows, serious annoyance to innocent persons. Instead-yousolve the mystery! We say, ‘A murder has occurred-thisis the criminal!’”

“And suppose I do not solve it?”

“Ah,mon cher!” M. Bouc’s voice became positively caressing. “I know your reputation. I know something of your methods. This is the ideal case for you. To look up the antecedents of all these people, to discover theirbona fides -all that takes time and endless inconvenience. But have I not heard you say often that to solve a case a man has only to lie back in his chair and think? Do that. Interview the passengers on the train, view the body, examine what clues there are, and then-well, I have faith in you! I am assured that it is no idle boast of yours. Lie back and think-use (as I have heard you say so often) the little grey cells of the mind-and you willknow!”

He leaned forward, looking affectionately at the detective.

“Your faith touches me, my friend,” said Poirot emotionally. “As you say, this cannot be a difficult case. I myself last night-but we will not speak of that now. In truth, this problem intrigues me. I was reflecting, not half an hour ago, that many hours of boredom lay ahead whilst we are stuck here. And now-a problem lies ready to my hand.”

“You accept then?” said M. Bouc eagerly.

“C’est entendu. You place the matter in my hands.”

“Good-we are all at your service.”

“To begin with, I should like a plan of the Istanbul-Calais coach, with a note of the people who occupied the several compartments, and I should also like to see their passports and their tickets.”