sticking his elbows on the table, lifting his arms, tapping the forefinger of his right hand against the forefinger of his left, and at the same time bringing his intent, gleaming eyes so close to the fingers that he almost grew cross-eyed.
âFirst of all, I myself can testify that there was no person in or on the tower â hiding there â when we left Mr Brooke alone. Such an idea is absurd! The place was as bare as a jug! I saw for myself! And the same truth applies to my return at five minutes past four, when I can take my oath that no murderer was lurking inside to make subsequent escape.
âNext, what happens as soon as Harry and I go away? The open grass space, surrounding the tower on every side except for the narrow segment where it overhangs the river, is instantly invaded by a family of eight persons: Monsieur and Madame Lambert, their niece, their daughter-in-law, and four children.
âI am a bachelor, thank God.
âThese people take possession of the open space. By sheer numbers they fill it. Papa and Mama are in sight of the doorway. Niece and eldest child keep walking round the tower and looking at it. The two youngest are actually inside . And all agree that no person either entered or left the tower during that time.â
Miles opened his mouth to make a protest, but Professor Rigaud intervened before he could speak.
âIt is true,â the professor conceded, âthat these people could not speak as to the side of the round-tower facing the river.â
âAh!â said Miles. âThere were no witnesses on that side?â
âAlas, none.â
âThen itâs fairly obvious, isnât it? You told us a while ago that one of the battlements round the parapet, on the side facing the river, had crumbling pieces of rock broken off as though someoneâs fingers had clawed at them in climbing up. The murderer must have come from the river-side.â
âConsider,â said Professor Rigaud in a persuasive voice, âthe difficulties of such a theory.â
âWhat difficulties?â
The other checked them off on his forefinger, tapping again.
âNo boat approached the tower, or it would have been seen. The stone of that tower, forty feet high, was as smooth as a wet fish. The lowest window (as measured by the police) was fully twenty-five feet above the surface of the water. How does your murderer scale the wall, kill Mr Brooke, and get down again?â
There was a long silence.
âBut, hang it all, the thing was done!â protested Miles. âYouâre not going to tell me this crime was committed by a â¦â
âBy a what?â
The question was fired back so quickly, while Professor Rigaud lowered his lands and leaned forward, that Miles felt an eerie and disturbing twinge of nerves. It seemed to him that Professor Rigaud was trying to tell him something, trying to lead him, trying to draw him on, with that sardonic amusement behind it.
âI was going to say,â Miles answered, âby some sort of supernatural being that could float in the air.â
âHow curious for you to use those words! How very interesting!â
âWould you mind if I interrupted for a moment?â asked Barbara, fiddling with the tablecloth. âThe main thing, after all, is about â is about Fay Seton. I think you said she had an appointment with Mr Brooke for four oâclock. Did she keep that appointment at all?â
âShe was, at least, not seen.â
â Did she keep that appointment, Professor Rigaud?â
âShe arrived there afterwards, mademoiselle. When it was all over.â
âThen what was she doing during that time?â
âAh!â said Professor Rigaud, with such relish that both his auditors half dreaded what he might say. âNow we come to it!â
âCome to what?â
âThe most fascinating part of the mystery. This puzzle of a man alone when he is