Starr very much wanted to know who drove an automobile without lights into isolated arroyos and over the desert trails at night.  He had not, strange to say, seen any machine with Silvertown cord tires in San Bonito or in Malpais, though he had given every car he saw the second glance to make sure.  He knew that such tires were something new and expensive, so much so that they were not in general use in that locality.  Even in El Paso they were rarely seen at that time, and only the fact that the great man who gave him his orders had happened to be using them on his machine, and had mentioned the fact to Starr, who was honored with his friendship, had caused Starr to be familiar with them and to recognize instantly the impress they left in soft soil.  It was a clue, and that was the best he could say for it.  It was just a little better than nothing, he decided.  What he wanted most was to see the machine itself at close range, and to see the men who rode in it—­and I am going to tell you why.

There was a secret political movement afoot in the Southwest; a movement hidden so far underground as to be practically unnoticed on the surface; but a movement, nevertheless, that had been felt and recorded by that political seismograph, the Secret Service of our Government.  It had been learned, no mere citizen may know just how, that the movement was called the Mexican Alliance.  It was suspected that the object was the restoration of three of our States to Mexico, their original owner.  Suspected, mind you; and when even the Secret Service can do no more than suspect, you will see how well hidden was the plot.  Its extent and its ramifications they could only guess at.  Its leaders no man could name, nor even those who might be suspected more than others.

But a general uprising in three States, in conjunction with, and under the control of, a concerted, far-sweeping revolution across the border, would not be a thing to laugh over.  Uncle Sam smiled tolerantly when some would have had him chastise.  Uncle Sam smiled, and watched, and waited and drummed his fingers while he read secret reports from men away out somewhere in Arizona, and New Mexico, and Texas, and urged them to burrow deeper and deeper underground, and to follow at any cost the molelike twistings and blind turnings of this plot to steal away three whole States in a lump.

Now you see, perhaps, why Starr was so curious about that automobile, and why he was interested in Estancio Medina, Mexican-American rancher who owned much land and many herds, and who was counted a power among his countrymen; who spoke English with what passed for fluency, and who had very decided and intelligent opinions upon political matters, and who boldly proclaimed his enthusiasm for the advancement of his own race.