But he left the rest of the conversation, as they wandered back to the house, to Antony.  He wanted to think.  There seemed to be no doubt now that Cayley was a villain.  Bill had never been familiar with a villain before.  It didn’t seem quite fair of Cayley, somehow; he was taking rather a mean advantage of his friends.  Lot of funny people there were in the world funny people with secrets.  Look at Tony, that first time he had met him in a tobacconist’s shop.  Anybody would have thought he was a tobacconist’s assistant.  And Cayley.  Anybody would have thought that Cayley was an ordinary decent sort of person.  And Mark.  Dash it! one could never be sure of anybody.  Now, Robert was different.  Everybody had always said that Robert was a shady fellow.

But what on earth had Miss Norris got to do with it?  What had Miss Norris got to do with it?  This was a question which Antony had already asked himself that afternoon, and it seemed to him now that he had found the answer.  As he lay in bed that night he reassembled his ideas, and looked at them in the new light which the events of the evening threw upon the dark corners in his brain.

Of course it was natural that Cayley should want to get rid of his guests as soon as the tragedy was discovered.  He would want this for their own sake as well as for his.  But he had been a little too quick about suggesting it, and about seeing the suggestion carried out.  They had been bustled off as soon as they could be packed.  The suggestion that they were in his hands, to go or stay as he wished, could have been left safely to them.  As it was, they had been given no alternative, and Miss Norris, who had proposed to catch an after-dinner train at the junction, in the obvious hope that she might have in this way a dramatic cross-examination at the hands of some keen-eyed detective, was encouraged tactfully, but quite firmly, to travel by the earlier train with the others.  Antony had felt that Cayley, in the tragedy which had suddenly befallen the house, ought to have been equally indifferent to her presence or absence.  But he was not; and Antony assumed from this that Cayley was very much alive to the necessity for her absence.

Why?

Well, that question was not to be answered off-hand.  But the fact that it was so had made Antony interested in her; and it was for this reason that he had followed up so alertly Bill’s casual mention of her in connection with the dressing-up business.  He felt that he wanted to know a little more about Miss Norris and the part she had played in the Red House circle.  By sheer luck, as it seemed to him, he had stumbled on the answer to his question.

Miss Norris was hurried away because she knew about the secret passage.

The passage, then, had something to do with the mystery of Robert’s death.  Miss Norris had used it in order to bring off her dramatic appearance as the ghost.  Possibly she had discovered it for herself; possibly Mark had revealed it to her secretly one day, never guessing that she would make so unkind a use of it later on; possibly Cayley, having been let into the joke of the dressing-up, had shown her how she could make her appearance on the bowling-green even more mysterious and supernatural.  One way or another, she knew about the secret passage.  So she must be hurried away.