“And, of course, that’s the quickest way of the three,” he said to himself.  “Through the hall, and out at the back; turn to the left and there you are.  Instead of which, we ran the longest way round the house.  Why?  Was it to give Mark more time in which to escape?  Only, in that case—­why run?  Also, how did Cayley know then that it was Mark who was trying to escape?  If he had guessed—­well, not guessed, but been afraid—­that one had shot the other, it was much more likely that Robert had shot Mark.  Indeed, he had admitted that this was what he thought.  The first thing he had said when he turned the body over was, ’Thank God!  I was afraid it was Mark.’  But why should he want to give Robert time in which to get away?  And again—­why run, if he did want to give him time?”

Antony went out of the house again to the lawns at the back, and sat down on a bench in view of the office windows.

“Now then,” he said, “let’s go through Cayley’s mind carefully, and see what we get.”

Cayley had been in the hall when Robert was shown into the office.  The servant goes off to look for Mark, and Cayley goes on with his book.  Mark comes down the stairs, warns Cayley to stand by in case he is wanted, and goes to meet his brother.  What does Cayley expect?  Possibly that he won’t be wanted at all; possibly that his advice may be wanted in the matter, say, of paying Robert’s debts, or getting him a passage back to Australia; possibly that his physical assistance may be wanted to get an obstreperous Robert out of the house.  Well, he sits there for a moment, and then goes into the library.  Why not?  He is still within reach, if wanted.  Suddenly he hears a pistol-shot.  A pistol-shot is the last noise you expect to hear in a country-house; very natural, then, that for the moment he would hardly realize what it was.  He listens—­and hears nothing more.  Perhaps it wasn’t a pistol-shot after all.  After a moment or two he goes to the library door again.  The profound silence makes him uneasy now.  Was it a pistol-shot?  Absurd!  Still—­no harm in going into the office on some excuse, just to reassure himself.  So he tries the door—­and finds it locked!

What are his emotions now?  Alarm, uncertainty.  Something is happening.  Incredible though it seems, it must have been a pistol-shot.  He is banging at the door and calling out to Mark, and there is no answer.  Alarm—­yes.  But alarm for whose safety?  Mark’s, obviously.  Robert is a stranger; Mark is an intimate friend.  Robert has written a letter that morning, the letter of a man in a dangerous temper.  Robert is the tough customer; Mark the highly civilized gentleman.  If there has been a quarrel, it is Robert who has shot Mark.  He bangs at the door again.

Of course, to Antony, coming suddenly upon this scene, Cayley’s conduct had seemed rather absurd, but then, just for the moment, Cayley had lost his head.  Anybody else might have done the same.  But, as soon as Antony suggested trying the windows, Cayley saw that that was the obvious thing to do.  So he leads the way to the windows—­the longest way.