"I suppose you opened the windows when you laid

him down on the bed, Hastings?''

"No, I didn't," I replied. "As far as I remember, they were shut."

Poirot lifted his head suddenly.

"Shut--and now they are open. What can that

mean?"

"Somebody came in that way," I suggested.

"Possibly," agreed Poirot, but he spoke absently and without conviction. After a minute or two he said:

"That is not exactly the point I had in mind, Hastings. If only one window was open it would not intrigue

me so much. It is both windows being open that strikes

me as curious."

THE BIG FOUR 17

He hurried into the other room.

"The sitting-room window is open, too. That also we left shut. Ah!"

He bent over the dead man, examining the corners of

the mouth minutely. Then he looked up suddenly.

"He has been gagged, Hastings. Gagged and then

poisoned."

"Good heavens!" I exclaimed, shocked. "I suppose we shall find out all about it from the postmortem."

"We shall find out nothing. He was killed by inhaling strong prussic acid. It was jammed right under his nose. Then the murderer went away again, first opening all

the windows. Hydrocyanic acid is exceedingly volatile,

but it has a pronounced smell of bitter almonds. With

no trace of the smell to guide them, and no suspicion of foul play, death would be put down to some natural

cause by the doctors. So this man was in the Secret Service, Hastings. And five years ago he disappeared in

Russia."

"The last two years he's been in the Asylum," I said.

"But what of the three years before that?"

Poirot shook his head, and then caught my arm.

"The clock, Hastings, look at the clock."

I followed his gaze to the mantelpiece. The dock had

stopped at four o'clock.

"Mon ami, some one has tampered with it. It had still three days to run. It is an eight-day clock, you comprehend?"

"But what should they want to do that for? Some

idea of a false scent by making the crime appear to have taken place at four o'clock?"

"No, no; rearrange your ideas, mon ami. Exercise

your little gray cells. You are Mayerling. You hear

something, perhaps--and you know well enough that

18 Agatha Christie

your doom is sealed. You have just time to leave a sign. Four o'clock, Hastings. Number Four, the destroyer. Ah! an idea!"

He rushed into the other room and seized the telephone.

He asked for Hanwell.

"You are the Asylum, yes7 I understand there has

been an escape to-day? What is that you say? A little

moment, if you please. Will you repeat that? Ah! parfaitement." He

hung up the receiver, and turned to me.

"You heard, Hastings? There has been no escape."

"But the man who came--the keeper?" I said.

"I wonder--I very much wonder."

"You mean--?"

"Number Four--the destroyer."

I gazed at Poirot dumbfounded. A minute or two

after, on recovering my voice, I said:-"We shall know him again, anywhere, that's one thing. He was a man of very pronounced personality."