ll wouldn't have killed anybody in cold blood himself,
and because he took it for granted that other people behaved pretty much
as he did. But Antony had no such illusions. Murders were done; murder
had actually been done here, for there was Robert's dead body. Why not
another murder?

Had Mark been in the office at all that afternoon? The only evidence
(other than Cayley's, which obviously did not count) was Elsie's. Elsie
was quite certain that she had heard his voice. But then Bill had said
that it was a very characteristic voice--an easy voice, therefore, to
imitate. If Bill could imitate it so successfully, why not Cayley?

But perhaps it had not been such a cold-blooded killing, after all.
Suppose Cayley had had a quarrel with his cousin that afternoon over the
girl whom they were both wooing. Suppose Cayley had killed Mark, either
purposely, in sudden passion, or accidentally, meaning only to knock
him down. Suppose that this had happened in the passage, say about
two o'clock, either because Cayley had deliberately led him there, or
because Mark had casually suggested a visit to it. (One could imagine
Mark continually gloating over that secret passage.) Suppose Cayley
there, with the body at his feet, feeling already the rope round his
neck; his mind darting this way and that in frantic search for a way
of escape; and suppose that suddenly and irrelevantly he remembers
that Robert is coming to the house at three o'clock that
afternoon--automatically he looks at his watch--in half an hour's
time.... In half an hour's time. He must think of something quickly,
quickly. Shall he bury the body in the passage and let it be thought
that Mark ran away, frightened at the mere thought of his brother's
arrival? But there was the evidence of the breakfast table. Mark had
seemed annoyed at this resurrection of the black sheep, but certainly
not frightened. No; that was much too thin a story. But suppose Mark had
actually seen his brother and had a quarrel with him; suppose it could
be made to look as if Robert had killed Mark--

Antony pictured to himself Cayley in the passage, standing over the dead
body of his cousin, and working it out. How could Robert be made to seem
the murderer, if Robert were alive to deny it? But suppose Robert were
dead, too?

He looks at his watch again. (Only twenty-five minutes now.) Suppose
Robert were dead, too? Robert dead in the office, and Mark dead in the
passage how does that help? Mad