“We might pick up the beam from the wetness underfoot,” he said, “but we’ll play it safe and use this too.”

They went on for a long way.  Lockley fumed, “I don’t like this!  We ought to be there—­”

“I think,” said Jill, “I smell it.”

“I’ll try it,” said Lockley.

He detected the jungle smell and its concomitant revolting odors.  He led Jill back.

“Wait here, by this big tree stump.  I’ll be able to find you and you’re safe enough from the beam.”

He turned away.  Jill said pleadingly, “Please be careful!”

“A little while ago,” he told her gloomily, “I felt that I had too much useful information to take any chances with my life, let alone yours.  I’m not so sure of my importance now.  But I think you still need somebody else around.”

“I do!” said Jill.  “And you know it!  I’d much rather—­”

“I’ll be back,” he repeated.

He went away, trailing the watch spring.

He was extra cautious now.  The smell recurred and grew stronger.  He began to feel the first faint flashes of light in his eyes.  It was the symptom which followed the smell when approaching a terror beam.  Then a faint, discordant murmur, originating in his own ears.  He turned on the device made of two graters and the elements of a pocket radio.  The smell ceased.  The faint flashes of light stopped.  There was no longer a raucous sound.

He turned off the ion producing device.  The symptoms returned.  He turned it on and off.  He took a step forward.  He tested again.  The cloud of ions from the innumerable jagged points was invisible, but somehow it refracted or reflected—­in any case, neutralized—­the weapon of the beings at Boulder Lake.  He went on and presently he felt the very faintest possible tingling of his skin and heard the barest whisper of a sound, and smelled the jungle reek as something so diluted that he was hardly sure he smelled it.

He went on, and those faint sensations ceased.  Presently, impatient of his own timorousness, he turned the device off again.  He had walked through the terror beam.

He started back with the device turned on once more and at the point where he’d felt the beam’s manifestations faintly, he stopped to savor his now seemingly useless triumph.  If the monsters had a detonating beam this meant nothing.  Yet it could have meant everything.  He paid close attention and distinctly but weakly experienced the effect of the terror beam.

Then he didn’t.  Not at all.  The sensations were cut off.

He heard Jill cry out shrilly.  He plunged toward the place where he had left her.  He raced.  He leaped.  Once he fell, and frantically swore at the wet stuff that had caused him to slip.  He reached the tree stump and Jill was not there.  He saw the saucer-sized tracks her feet had made on the saturated fallen leaves.  They led toward the road.

He heard a car door slam and a motor roar.  He plunged onward more desperately than before.