Apparently they felt safe, close though they were to the line.  Indeed, they were safe enough—­from horsemen riding down from the Rolling R. So far they had thieved at their leisure and with impunity.  The element of risk had been discounted until they no longer considered it at all, except when they were actually within the Rolling R Boundaries.  Now, in the heat of the day, they slept as was their habit.  Even the herder was probably dozing in the saddle and leaving watchfulness to his cow-pony.  Certainly he did not give any sign that he saw the airplane as it glided silently over so that they could come back from the south.

“What I want, Bland, is to scare these horses back toward home,” Johnny said.  “We’ll come at ’em first from the south, and if they don’t run straight, we’ll have to circle round till they do.  But I want to come within shooting distance of them hombres under the trees.  See?  So fly as low as yuh dare, when we come back.”

Bland threw on the motor, circled and came volplaning back.  He did not complain; he left that for times when he was not flying.  Johnny braced himself, rifle ready.  He was sorry then that he was not an expert shot; but he hoped that luck would be with him and make up for what he lacked in skill.

The horses stampeded, carrying the herder with them.  They ran north, in a panic that would keep them going for some time.  As they raced clattering past the camp, Johnny saw four men rise up hastily, their faces turned up to the sky.  He leaned, took what aim was possible, and fired four shots as the plane swept over.

He did not hit any one, so far as he could see, but he saw them duck and run close to the tree trunks, which gave him some satisfaction.  Moreover, they were afoot.  Not a single horse remained within sight or hearing of that camp.

Johnny did not go back for another try at them, though he was tempted to land and fight it out with them.  There was Mary V to think of, and there were the horses.  They went on, shying off from the fleeing animals lest they drive them back instead of forward.  Bland spiraled upward, waiting to see what Johnny wanted next.  Whatever it might be, Bland would do it—­with two guns and a headstrong young man just behind him.

The thrum of the motor stuttered a little on the last upward turn.  Bland straightened out the plane, fussed with the spark and the gas, banked cautiously around and headed for home.  Like a heart that skips a beat now and then, an odd little pause, scarcely to be distinguished except when the ear has become accustomed to the rhythm of perfect firing, manifested itself.  Bland turned his head sidewise, listening.  The pause became more marked.  The steady, forward thrust slackened a little.  Johnny was aware that the monotonous waste below did not slip behind them quite so fast; not quite.

Bland was nursing the motor along, Johnny could tell by his slight movements.  It seemed to him that a tenseness had crept into the set of Bland’s head.  Johnny braced himself for something—­just what, he did not know.  His knowledge of motors was superficial.  Something was wrong with the ignition, he guessed, but he had no idea what it could be.