ylva West, my fiancee, in violation of regulations. I ask
that her family be notified."

He snapped off the lights and went with her. The red rocket-ship had
landed in the very next valley. There was a glare there, which wavered
and flickered and died away.

"Martians!" said Thorn in fine irony. "We'll see when the Watch planes
come! My guess is Com-Pubs, using a searchlight! Nervy!"

The glare vanished. There was only silence, a curiously complete and
deadly silence. And Thorn said, suddenly:

"There's no wind!"

There was not. Not a breath of air. The mountains were uncannily
quiet. The air was impossibly still, for a mountain-top. Ten minutes
went by. Twenty. The detector-whistles shrilled.

"There's the Watch," said Thorn in satisfaction. "Now we'll see!"

And then, abruptly, there was a lurid flash in the sky to northward.
Two thousand feet up and a mile away, the unearthly green blaze of a
hexynitrate explosion lit the whole earth with unbearable brilliance.

"Stop your ears!" snapped Thorn.

* * * * *

The racking concussion-wave of hexynitrate will break human eardrums
at an incredible distance. But no sound came, though the seconds went
by.... Then, two miles away, there was a second gigantic flash....
Then a third.... But there was no sound at all. The quiet of the hills
remained unbroken, though Thorn knew that such cataclysmic detonations
should be audible at twenty miles or more. Then lights flashed on
above. Two--three--six of them. They wavered all about, darting here
and there.... Then one of the flying searchlights vanished utterly in
a fourth terrific flash of green.

"The watch planes are going up!" said Thorn dazedly. "Blowing up! And
we can't hear the explosions!"

Behind him the G.C. speaker barked his call. He raced to get its
message.

"The Watch planes we sent to join you," said a curt voice he
recognized as that of the Commanding General of the United Nations,
"have located an invisible barrier by their sonic altimeters. Four of
them seem to have rammed it and exploded without destroying it. What
have you to report?"

"I've seen the flashes, sir," said Thorn unsteadily, "but they made no
noise. And there's no wind, sir. Not a breath since the blue flash I
reported."

A pause.

"Your statement bears out their report," said the G.C. speaker
harshly. "The barrier seems to be hemispherical. No such barrier is
known on Earth. These must be Martian