Once, on an afternoon like this, he had ridden into town with a prisoner beside him, a youth whose lightning-swift hand had snuffed out a score of lives to avenge the killing of a friend.  The collector recalled that on that day he had ridden his favorite horse, a deep-chested buckskin, slender legged, and swift, with a strain of thoroughbred.

Beyond the little square of window through which he gazed lay the same kind of a road—­dusty, sun-white, edged with low brush.  And down the road, pace for pace with his thoughts, strode a buckskin horse, ridden by a man road-weary, gray with dust.  Beside him rode a youth, his head bowed and his hands clasped on the saddle-horn as though manacled.

“Jack!”

The assistant shoved back his chair and came to the window.

“There’s the rest of your picture,” said the collector.

As the assistant gazed at the riders, the collector stepped to his desk and buckled on a gun.

“Want to meet Waring?” he queried.

“I’m on for the next dance, Pat.”

The collector stepped out.  Waring reined up.  A stray breeze fluttered the flag above the custom-house.  Waring gravely lifted his sombrero.

“You’re under arrest,” said the collector.

Waring gestured toward Ramon.

“You, too,” nodded Pat.  “Get the kid and his horse out of sight,” he told the assistant.

Ramon, too weary to expostulate, followed the assistant to a corral back of the building.

The collector turned to Waring.  “And now, Jim, what’s the row?”

“Down the street—­and coming,” said Waring, as the rurales boiled from the cantina.

“We’ll meet ’em halfway,” said the collector.

And midway between the custom-house and the cantina the two cool-eyed, deliberate men of the North faced the hot-blooded Southern haste that demanded Waring as prisoner.  The collector, addressing the leader of the rurales, suggested that they talk it over in the cantina.  “And don’t forget you’re on the wrong side of the line,” he added.

The Captain of rurales and one of his men dismounted and followed the Americans into the cantina.  The leader of the rurales immediately exhibited a warrant for the arrest of Waring, signed by a high official and sealed with the great seal of Mexico.  The collector returned the warrant to the captain.

“That’s all right, amigo, but this man is already under arrest.”

“By whose authority?”

“Mine—­representing the United States.”

“The warrant of the Presidente antedates your action,” said the captain.

“Correct, Senor Capitan.  But my action, being just about two jumps ahead of your warrant, wins the race, I reckon.”

“It is a trick!”

“Si!  You must have guessed it.”

“I shall report to my Government.  And I also demand that you surrender to me one Ramon Ortego, of Sonora, who aided this man to escape, and who is reported to have killed one of my men and stolen one of my horses.”