They came to a sere, bare hillside on which neither trees nor brushwood grew.  It amounted to a natural clearing, acres in extent.  Lockley swept his eyes around.  There were many thick-foliaged small trees attempting to advance into the clear space.  He grunted in satisfaction.

“Sit down and rest,” he commanded.  “I’ll send a message.”

He broke off branches from dark green conifers.  He went out into the clearing and began to lay them out in a pattern.  He came back and broke off more, and still more.  Very slowly, because the lines had to be large and thick, the letters S.O.S. appeared in dark green on the clayey open space.  The letters were thirty feet high, and the lines were five feet wide.  They should show distinctly from the air.

“I think,” said Lockley with satisfaction, “that we might get something out of this!  If it’s sighted, a ’copter might risk coming in after us.”  He looked at her appraisingly.  “I think you’d enjoy a good meal.”

“I want to say something,” said Jill carefully.  “I think you’ve been trying to cheer me up, after saying something to arouse me—­which I needed.  If the creatures aren’t monsters, they’ll never actually let anybody loose who’s seen that they aren’t.  Isn’t that true?  And if it is—­”

“We know of six men who were captured,” insisted Lockley, “and I was one of them.  All six escaped.  Vale may have escaped.  They’re not good at keeping prisoners.  We don’t know and can’t know unless it’s mentioned on a news broadcast that he’s out and away.  So there’s absolutely no reason to assume that Vale is dead.”

“But if he saw them, when he was fighting them—­”

“The evidence,” insisted Lockley again, “is that he saw monsters.  The only reason to doubt it is that they blindfolded four of us.”

Jill seemed to think very hard.  Presently she said resolutely, “I’m going to keep on hoping anyhow!”

“Good girl!” said Lockley.

They waited.  He was impatient, both with fate and with himself.  He felt that he’d made Jill face reality when—­if this S.O.S. signal brought help—­it wasn’t necessary.  And there was enough of grimness in the present situation to make it cruelty.

After a very long time they heard a faint droning in the air.  There might have been others when they were trudging over bad terrain, and they might not have noticed because they were not listening for such sounds.  There were planes aloft all around the lake area.  They’d been sent up originally in response to a radar warning of something coming in from space.  Now they flew in vast circles around the landing place of that reported object.  They flew high, so high that only contrails would have pointed them out.  But atmospheric conditions today were such that contrails did not form.  The planes were invisible from the ground.

But the pilots could see.  When one patrol group was relieved by another, it carried high-magnification photographs of all the park, to be developed and examined with magnifying glasses for any signs of activity by the crew of the object from space.