everything in the kindest way."

"Oh, well, that's all right, then, and you must go to tea with Cynthia
another day."

I told him about the letter.

"I am sorry for that," he said. "I always had hopes of that letter. But
no, it was not to be. This affair must all be unravelled from within."
He tapped his forehead. "These little grey cells. It is 'up to them'--as
you say over here." Then, suddenly, he asked: "Are you a judge of
finger-marks, my friend?"

"No," I said, rather surprised, "I know that there are no two
finger-marks alike, but that's as far as my science goes."

"Exactly."

He unlocked a little drawer, and took out some photographs which he laid
on the table.

"I have numbered them, 1, 2, 3. Will you describe them to me?"

I studied the proofs attentively.

"All greatly magnified, I see. No. 1, I should say, are a man's
finger-prints; thumb and first finger. No. 2 are a lady's; they are much
smaller, and quite different in every way. No. 3"--I paused for some
time--"there seem to be a lot of confused finger-marks, but here, very
distinctly, are No. 1's."

"Overlapping the others?"

"Yes."

"You recognize them beyond fail?"

"Oh, yes; they are identical."

Poirot nodded, and gently taking the photographs from me locked them up
again.

"I suppose," I said, "that as usual, you are not going to explain?"

"On the contrary. No. 1 were the finger-prints of Monsieur Lawrence. No.
2 were those of Mademoiselle Cynthia. They are not important. I merely
obtained them for comparison. No. 3 is a little more complicated."

"Yes?"

"It is, as you see, highly magnified. You may have noticed a sort of
blur extending all across the picture. I will not describe to you
the special apparatus, dusting powder, etc., which I used. It is a
well-known process to the police, and by means of it you can obtain a
photograph of the finger-prints of any object in a very short space of
time. Well, my friend, you have seen the finger-marks--it remains to
tell you the particular object on which they had been left."

"Go on--I am really excited."

"Eh bien! Photo No. 3 represents the highly magnified surface of a tiny
bottle in the top poison cupboard of the dispensary in the Red Cross
Hospital at Tadminster--which sounds like the house that Jack built!"

"Good heavens!" I exclaimed. "But what were Lawrence Cavendish's
finger-marks doing on it? He never went near the poison cupboard the day
we were there!"

"Oh, y