"What's what?" inquired Ned.

"That sound? Don't you hear it? Listen!"

"It's an airship--maybe yours coming back!" cried the young
banker.

As he spoke Ned did hear, seemingly in the air above the house, a
curious, throbbing, pulsating sound.

"That's so! It is an airship motor!" exclaimed Tom. "Come on out!"

Together they rushed from the house, but, ere they reached the
yard, the sound had ceased. They looked up into the sky, but could
see nothing, though the night was light from a full moon.

"I certainly heard it," said Tom.

"So did I," asserted Ned. "But where is it now?"

They advanced toward the group of work-buildings. Something
showing white in the moonlight, before the hangar, caught Ned's
eyes.

"Look!" he exclaimed. "There's an airship, Tom!"

The two rushed over to the level landing place before the big
shed. And there, as if she had just been run out for a flight, was
the Eagle. She had come back in the night, as mysteriously as she