He came back.  As he came, he wound something into a little coil.  It was the silicon bronze mainspring of his non-magnetic watch.  He held it for her to see and put it in his pocket.

“I know what the terror beam is—­for what good it’ll do!” he said bitterly.  “It’s a beam of radiation on the order of radar, and for that matter X-rays and everything else.  Only an aerial does pick it up and this watchspring makes a good one.  I could barely detect the smell at a certain place, but when I touched the laid out spring, it picked up more than my body did and it became horrible!  Then I moved in to where my skin began to tingle and I saw lights and heard noises.  The spring made all the difference in the world.  I even found the direction of the beam.”

Jill looked frightened.

“It comes from Boulder Lake,” he told her.  “It’s the terror beam, all right!  You can walk into it without knowing it.  And I suspect that if it were strong enough it would be a death ray, too!”

Jill seemed to flinch a little.

“They’re not using it at killing strength,” said Lockley coldly.  “They’re softening us up.  Letting us find out we’re frustrated and helpless, and then letting us think it over.  I’ll bet they intended the four of us to escape from that compost pit thing so we could tell about it!  But we’ll know, now, if we find dead men in rows in a wiped-out town, we’ll know what killed them, and when they ask us politely to become their slaves, we’ll know we’ll have to do it or die!”

Jill waited.  When he seemed to have finished, she said, “If they’re monsters, do you think they want to enslave us?”

He hesitated, and then said with a grimace, “I’ve a habit, Jill, of looking forward to the future and expecting unpleasant things to happen.  Maybe it’s so I’ll be pleasantly surprised when they don’t.”

“Suppose,” said Jill, “that they aren’t monsters.  What then?”

“Then,” said Lockley, “it’s a cold war device, to find out if the other side in the cold war can take us over without our suspecting they’re the ones doing it.  Naturally those in this ship will blow themselves up rather than be found out.”

“Which,” said Jill steadily, “doesn’t offer much hope for....”

She didn’t say Vale’s name.  She couldn’t.  Lockley grimaced again.

“It’s not certain, Jill.  The evidence is on the side of the monsters.  But in either case the thing for us to do is get to the Army with what I’ve found out.  I’ve had a stationary beam to test, however crudely.  The cordon must have been pushed back by a moving or an intermittent beam.  It wouldn’t be easy to experiment with one of those.  Come on.”

She stood up.  She followed when he went on.  They climbed steep hillsides and went down into winding valleys.  The sun began to sink in the west.  The going was rough.  For Lockley, accustomed to wilderness travel, it was fatiguing.  For Jill it was much worse.