"It will be worse if his machine is out of order and he is coming back to fuss over it." "We must make our break now," Prescott whispered.
"Lead the way," answered Reade.

Fortunately, at this moment, the sentries were at the outer ends of their posts.

Bending low, keeping his gaze on the sentries, Dick scurried noiselessly over the ground until he paused, erect and panting, under the shadow of the building near the rear.
So far safe, for Reade was with him an instant later.

While the rear sentry finished his post at this end just beyond the hangar, the front sentry, as far as had been observed, came only as far as the sliding doors of the hangar.
"Get your automatic ready!" Dick whispered.

Then they heard the rear sentry coming toward them.
There came that tense instant when the sentry's passing form loomed up within three feet of Captain Prescott.