He took no orders save such general ones as Senator Warfield had just given him.

He gave none.

Whatever he did he did alone, and he took no man into his confidence.

It is more than probable that Senator Warfield would never have known to a certainty that Al was responsible for Thurman's death, if Al had not been worried over the Quirt's possible knowledge of the crime and anxious to know just how far his power might go.
Ostensibly he was in charge of the camp at Whisper, a place far enough off the beaten trails to free him from chance visitors.

The Sawtooth kept many such camps occupied by men whose duty it was to look after the Sawtooth cattle that grazed near; to see that stock did not "bog down" in the tricky sand of the adjacent water holes and die before help came, and to fend off any encroachments of the smaller cattle owners,--though these were growing fewer year by year, thanks to the weeding-out policy of the Sawtooth and the cunning activities of such as Al Woodruff.
It may sound strange to say that the Sawtooth country had not had a real "killing" for years, though accidental deaths had been rather frequent.
One man, for instance, had fallen over a ledge and broken his neck, presumably while drunk.