" it ? '' I asked solicitously " ill, I trust ? ''

"No, no, not ill But I decide an affair of great moment ''

"Whether to catch the criminal or not ? '' I asked facetiously

But, to my great surprise, Poirot nodded gravely

" ' or not ,' so great Shakespeare says, ' question ' ''

trouble to correct the quotation

" serious, Poirot ? ''

" most serious most serious of all things hangs balance ''

" is ? ''

"A woman's happiness, mon ami,'' gravely

quite know what

"The moment ,'' said Poirot thoughtfully, "and know what For, see you, big stake I play No one but I, Hercule Poirot, would attempt it ! '' And he tapped himself proudly breast

After pausing respectfully, so as not to spoil his effect, him Lawrence's message

"Aha ! '' he cried "So he has found the extra coffee-cup good He has more intelligence than would appear, this long-faced Monsieur Lawrence of yours ! ''

myself think very highly of Lawrence's intelligence; but I forebore to contradict Poirot, and gently took him to task for forgetting my instructions as were Cynthia's days off

" true the head of sieve However, the other young lady was most kind She was sorry disappointment, and showed me everything kindest way ''

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

him letter

" sorry ,'' "I always had hopes letter But no, not This affair must all be unravelled from within '' He tapped his forehead "These little grey cells 'up ' -- say over here '' Then, suddenly, he asked: " judge of finger-marks, my friend ? ''

"No,'' , rather surprised, " no two finger-marks alike, but that's as far as my science goes ''

"Exactly ''

He unlocked little drawer, and took out some photographs which he laid table

" numbered them, 1, 2, 3 describe them ? ''

I studied the proofs attentively

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

"Overlapping the others ? ''

"Yes ''

"You recognize them beyond fail ? ''

"Oh, yes; identical ''

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

"I suppose,'' , "that as usual, going to explain ? ''

" contrary No 1 were the finger-prints of Monsieur Lawrence No 2 were those of Mademoiselle Cynthia important I merely obtained them for comparison No 3 is little more complicated ''

"Yes ? ''

" , as , highly magnified noticed sort of blur extending all across the picture describe the special apparatus, dusting powder, etc , which I used well-known process police, and of it obtain photograph finger-prints of any object in very short space Well, my friend, seen the finger-marks -- it remains you the particular object they left ''

"Go on -- really excited ''

"Eh bien ! Photo No 3 represents the highly magnified surface of tiny bottle top poison cupboard dispensary 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 ? He never went near the poison cupboard the day we were there ! ''

"Oh, yes, ! ''

"Impossible ! We were all together the whole time ''

Poirot shook his head

"No, my friend, moment all together moment when been all together, or it necessary to Monsieur Lawrence and join you balcony ''

"I'd forgotten that,'' I admitted "But only for moment ''

"Long enough ''

"Long enough for what ? ''

Poirot's smile became rather enigmatical

"Long enough for gentleman who had once studied medicine to gratify very natural interest and curiosity ''

Our eyes met Poirot's were pleasantly vague He got up and hummed little tune I watched him suspiciously

"Poirot,'' , " particular little bottle ? ''

Poirot looked window

"Hydro-chloride of strychnine,'' , over his shoulder, continuing to hum

"Good heavens ! '' it quite quietly not surprised I had expected that answer

"They use the pure hydro-chloride of strychnine very little -- only occasionally for pills official solution, Liq Strychnine Hydro-clor used in most medicines why the finger-marks have remained undisturbed since then ''

"How did you manage this photograph ? ''

"I dropped my hat balcony,'' explained Poirot simply "Visitors permitted below hour, so, many apologies, Mademoiselle Cynthia's colleague had down and fetch it ''

"Then what you were going ? ''

"No, not at all I merely realized possible, from your story, for Monsieur Lawrence poison cupboard The possibility had confirmed, or eliminated ''

"Poirot,'' , "your gaiety deceive me discovery ''

" know,'' said Poirot "But does strike me it has struck you too ''

"What ? ''

"Why, altogether strychnine case third time we run up against it strychnine in Mrs Inglethorp's tonic the strychnine sold across the counter at Styles St Mary by Mace Now more strychnine, handled by household confusing; and, , like confusion ''

Before reply, other Belgians opened the door and stuck his head in

" lady below, asking Hastings ''

"A lady ? ''

I jumped up Poirot followed me down the narrow stairs Mary Cavendish was standing doorway

" visiting an old woman village,'' she explained, "and as Lawrence told me you were with Monsieur Poirot call ''

"Alas, madame,'' said Poirot, " you had come to honour me with visit ! ''

" some day, ask me,'' she promised him, smiling

" well If need father confessor, madame'' -- she started ever so slightly -- "remember, Papa Poirot is always at your service ''

She stared at him , seeking to read some deeper meaning into his words Then she turned abruptly away

"Come, not walk back too, Monsieur Poirot ? ''

"Enchanted, madame ''

All the way to Styles, Mary talked fast and feverishly It struck me that in some way she was nervous of Poirot's eyes

The weather had broken, sharp wind was almost autumnal in its shrewishness Mary shivered little, and buttoned her black sports coat closer The wind trees made mournful noise, like some great giant sighing

We walked great door of Styles, and at once the knowledge came that something was wrong

Dorcas came running out to meet us She was crying and wringing her hands aware of other servants huddled together background, all eyes and ears

"Oh, m'am ! Oh, m'am ! I don't know how you -- ''

" it, Dorcas ? '' I asked impatiently "Tell us at once ''

"It's those wicked detectives They've arrested him -- they've arrested Mr Cavendish ! ''

"Arrested Lawrence ? '' I gasped

strange look come into Dorcas's eyes

"No, sir Not Mr Lawrence -- Mr John ''