Why?  To give the murderer time to escape?  If he had thought then that Mark was the murderer, perhaps, yes.  But he thinks that Robert is the murderer.  If he is not hiding anything, he must think so.  Indeed he says so, when he sees the body; “I was afraid it was Mark,” he says, when he finds that it is Robert who is killed.  No reason, then, for wishing to gain time.  On the contrary, every instinct would urge him to get into the room as quickly as possible, and seize the wicked Robert.  Yet he goes the longest way round.  Why?  And then, why run?

“That’s the question,” said Antony to himself, as he filled his pipe, “and bless me if I know the answer.  It may be, of course, that Cayley is just a coward.  He was in no hurry to get close to Robert’s revolver, and yet wanted me to think that he was bursting with eagerness.  That would explain it, but then that makes Cayley out a coward.  Is he?  At any rate he pushed his face up against the window bravely enough.  No, I want a better answer than that.”

He sat there with his unlit pipe in his hand, thinking.  There were one or two other things in the back of his brain, waiting to be taken out and looked at.  For the moment he left them undisturbed.  They would come back to him later when he wanted them.

He laughed suddenly, and lit his pipe.

“I was wanting a new profession,” he thought, “and now I’ve found it.  Antony Gillingham, our own private sleuthhound.  I shall begin to-day.”

Whatever Antony Gillingham’s other qualifications for his new profession, he had at any rate a brain which worked clearly and quickly.  And this clear brain of his had already told him that he was the only person in the house at that moment who was unhandicapped in the search for truth.  The inspector had arrived in it to find a man dead and a man missing.  It was extremely probable, no doubt, that the missing man had shot the dead man.  But it was more than extremely probable, it was almost certain that the Inspector would start with the idea that this extremely probable solution was the one true solution, and that, in consequence, he would be less disposed to consider without prejudice any other solution.  As regards all the rest of them —­Cayley, the guests, the servants—­they also were prejudiced; in favour of Mark (or possibly, for all he knew, against Mark); in favour of, or against, each other; they had formed some previous opinion, from what had been said that morning, of the sort of man Robert was.  No one of them could consider the matter with an unbiased mind.

But Antony could.  He knew nothing about Mark; he knew nothing about Robert.  He had seen the dead man before he was told who the dead man was.  He knew that a tragedy had happened before he knew that anybody was missing.  Those first impressions, which are so vitally important, had been received solely on the merits of the case; they were founded on the evidence of his senses, not on the evidence of his emotions or of other people’s senses.  He was in a much better position for getting at the truth than was the Inspector.