ence, Mary Cavendish's conduct was just as
inexplicable. But if, on the other hand, it was John, the whole thing
was explained quite naturally."

"So," I cried, a light breaking in upon me, "it was John who quarrelled
with his mother that afternoon?"

"Exactly."

"And you have known this all along?"

"Certainly. Mrs. Cavendish's behaviour could only be explained that
way."

"And yet you say he may be acquitted?"

Poirot shrugged his shoulders.

"Certainly I do. At the police court proceedings, we shall hear the case
for the prosecution, but in all probability his solicitors will advise
him to reserve his defence. That will be sprung upon us at the trial.
And--ah, by the way, I have a word of caution to give you, my friend. I
must not appear in the case."

"What?"

"No. Officially, I have nothing to do with it. Until I have found that
last link in my chain, I must remain behind the scenes. Mrs. Cavendish
must think I am working for her husband, not against him."

"I say, that's playing it a bit low down," I protested.

"Not at all. We have to deal with a most clever and unscrupulous man,
and we must use any means in our power--otherwise he will slip
through our fingers. That is why I have been careful to remain in the
background. All the discoveries have been made by Japp, and Japp will
take all the credit. If I am called upon to give evidence at all"--he
smiled broadly--"it will probably be as a witness for the defence."

I could hardly believe my ears.

"It is quite en regle," continued Poirot. "Strangely enough, I can give
evidence that will demolish one contention of the prosecution."

"Which one?"

"The one that relates to the destruction of the will. John Cavendish did
not destroy that will."

Poirot was a true prophet. I will not go into the details of the police
court proceedings, as it involves many tiresome repetitions. I will
merely state baldly that John Cavendish reserved his defence, and was
duly committed for trial.

September found us all in London. Mary took a house in Kensington,
Poirot being included in the family party.

I myself had been given a job at the War Office, so was able to see them
continually.

As the weeks went by, the state of Poirot's nerves grew worse and worse.
That "last link" he talked about was still lacking. Privately, I hoped
it might remain so, for what happiness could there be for Mary, if John
were not acquitted?

On September 15th John Cavendish ap