Up and down his room Kirby paced a beat from the window to the door and back again.  His mind was busy dissecting, analyzing, classifying.  Some one had once remarked that he had a single-track mind.  In one sense he had.  The habit of it was to follow a train of thought to its logical conclusion.  He did not hop from one thing to another inconsequently.

Just now his brain was working on his cousin James.  He went back to the first day of his arrival in Denver and sifted the evidence for and against him.  A stream of details, fugitive impressions, and mental reactions flooded through.

For one of so cold a temperament James had been distinctly friendly to him.  He had gone out of his way to find bond for him when he had been arrested.  He had tried to smooth over difficulties between him and Jack.  But Kirby, against his desire, found practical reasons of policy to explain these overtures.  James had known he would soon be released through the efforts of other cattlemen.  He had stepped in to win the Wyoming cousin’s confidence in order that he might prove an asset rather than a liability to his cause.  The oil broker had readily agreed to protect Esther McLean from publicity, but the reason for his forbearance was quite plain now.  He had been protecting himself, not her.

The man’s relation to Esther proved him selfish and without principle.  He had been willing to let his dead uncle bear the odium of his misdeed.  Yet beneath the surface of his cold manner James was probably swept by heady passions.  His love for Phyllis Harriman had carried him beyond prudence, beyond honor.  He had duped the uncle whose good-will he had carefully fostered for many years, and at the hour of his uncle’s death he had been due to reap the whirlwind.

The problem sifted down to two factors.  One was the time element.  The other was the temperament of James.  A man may be unprincipled and yet draw the line at murder.  He may be a seducer and still lack the courage and the cowardice for a cold-blooded killing.  Kirby had studied his cousin, but the man was more or less of a sphinx to him.  Behind those cold, calculating eyes what was he thinking?

Only once had he seen him thrown off his poise.  That was when Kirby and Rose had met him coming out of the Paradox white and shaken, his arm wrenched and strained.  He had been nonplussed at sight of them.  For a moment he had let his eyes mirror the dismay of his soul.  The explanation he had given was quite inadequate as a cause.

Twenty-four hours later Kirby had discovered the dead body of the Japanese valet Horikawa.  The man had been dead perhaps a day.  More hours than one had been spent by Kirby pondering on the possible connection of his cousin’s momentary breakdown and the servant’s death. Had James come fresh from the murder of Horikawa?