A second lieutenant spotted the S.O.S. within half an hour of the films’ return.  There was an immediate and intense conference.  The lengths of shadows were measured.  The size and slope and probable condition of the clearing’s surface were estimated.

A very light plane, intended for artillery-spotting, took off from the nearest airfield to Boulder Lake.

And Lockley and Jill heard it long before it came in sight.  It flew low, threading its way among valleys and past mountain-flanks to avoid being spotted against the sky.  The two beside the clearing heard it first as a faint mutter.  The sound increased, diminished, then increased again.

It shot over a minor mountain-flank and surveyed the bare space with the huge letters on it.  Lockley and Jill raced out into view, waving frantically.  The plane circled and circled, estimating the landing conditions.  It swung away to arrive at a satisfactory approach path.

It wavered.  It made a half-wingover, and it side-slipped crazily, and came up and stalled and flipped on its back and dived....

And it came out of its insane antics barely twenty feet above the ground.  It raced away as close as possible to touching its wheels to earth.  It went away behind the mountains.  The sound of its going dwindled and dwindled and was gone.  It appeared to have escaped from a deliberately set trap.

Lockley stared after it.  Then he went white.

“Idiot!” he cried fiercely.  “Come on!  Run!”

He seized Jill’s hand.  They fled together.  Evidently, something had played upon the pilot of the light plane.  He’d been deafened and blinded and all his senses were a shrieking tumult while his muscles knotted and his hands froze on the controls of his ship.  He hadn’t flown out of the beam that made him helpless.  He’d fallen out of it.  And then he raced for the horizon.  He got away.  And it would appear to those to whom he reported that he’d arrived too late at the distress-signal.  If fugitives had made it, they’d been overtaken and captured by the creatures of Boulder Lake, and there’d been an ambush set up for the plane.  It was a reasonable decision.

But it puzzled the pilot’s superior officers that he hadn’t been allowed to land the plane before the beam was turned on him.  He could have been paralyzed while on the ground, and he and his plane could have yielded considerable information to creatures from another world.  It was puzzling.

Lockley and Jill raced for the woodland at the clearing’s edge.  Lockley clamped his lips tight shut to waste no breath in speech.  The arrival and the circling of the plane had been a public notice that there were fugitives here.  If the beam could paralyze a pilot in mid-air, it could be aimed at fugitives on the ground....  There could be no faintest hope....

Wholly desperate, Lockley helped Jill down a hillside and into a valley leading still farther down.