"A most unusual type of woman, that," remarked Poirot, as we walked away.

"Madame Olivier? Yes, she--"

"Mais non, not Madame Olivier. Cela va sans dire! There are not many geniuses of her stamp in the world.

No, I referred to the other lady--the lady on the stairs."

"I didn't see her face," I said, staring. "And I hardly see how you could have done. She never looked at us."

"That is why I said she was an unusual type," said Poirot placidly. "A woman who enters her home--for I presume that it is her home since she enters with a

key--and runs straight upstairs without even looking at

two strange visitors in the hall to see who they are, is a very unusual type of woman--quite unnatural, in fact. Mille tonnerres! what is that?"

He dragged me back--just in time. A tree had crashed

down on to the side walk, just missing us. Poirot stared at it, pale and upset.

"It was a near thing that! But clumsy, all the same-for I had no suspicion--at least hardly any suspicion. Yes, but for my quick eyes, the eyes of a cat, Hercule

Poirot might now be crushed out of existence--a terrible calamity for the world. And you, too, mon ami--though that would not be such a national catastrophe."

"Thank you," I said coldly. "And what are we going to do now?"

"Do?" cried Poirot. "We are going to think. Yes, here and now, we are going to exercise our little gray

cells. This M. Halliday now, was he really in Paris? Yes, for Professor Bourgoneau, who knows him, saw and

spoke to him."

54 Agatha Christie

"What on earth are you driving at?" I cried.

"That was Friday morning. He was last seen at eleven Friday night--but was he seen then?"

"The porter--"

"A night porter--who had not previously seen Halliday. A man comes in, sufficiently like Halliday--we

may trust Number Four for that--asks for letters, goes

upstairs, packs a small suit-case, and slips out the next morning. Nobody saw Halliday all that evening--no,

because he was already in the hands of his enemies. Was

it Halliday whom Madame Olivier received? Yes, for

though she did not know him by sight, an impostor

could hardly deceive her on her own special subject. He

came here, he had his interview, he left. What happened

next?"

Seizing me by the arm, Poirot was fairly dragging me

back to the villa.

"Now, mon ami, imagine that it is the day after the disappearance, and that we are tracking footprints. You

love footprints, do you not? See--here they go, a

man's, Mr. Halliday's. ... He turns to the right as we

did, he walks briskly--ah! other footsteps following

behind--very quickly--small footsteps, a woman's.

See, she catches him up--a slim young woman, in a

widow's veil. 'Pardon, monsieur, Madame Olivier desires

that I recall you.' He stops, he turns. Now where

would the young woman take him? She does not wish to

be seen walking with him. Is it coincidence that she