the cold voice of Roger, speaking from the
empty air.

"You are over-wrought, Miss Marsden. You can be of no use to yourself or
to me in that condition. I command you to rest; and, to insure that
rest, you may pull that cord, which will establish about this room an
ether wall: a wall to cut off even this my voice...."

The voice ceased as she pulled the cord savagely and threw herself upon
a divan in a torrent of gasping, strangling, but rebellious sobs. Then
again came a voice, but not to her ears. Deep within her, pervading
every bone and muscle, it made itself felt rather than heard.

"Clio?" it asked. "Don't talk yet...."

"Conway!" she gasped in relief, every fiber of her being thrilled into
new hope at the deep, well-remembered voice of Conway Costigan.

"Keep still!" he snapped. "Don't act so happy! He may have a spy-ray on
you. He can't hear me, but he may be able to hear you. When he was
talking to you you must have noticed a sort of rough, sandpapery feeling
under that necklace I gave you? Since he's got an ether-wall around you
the beads are dead now. If you feel anything like that under the
wrist-watch, breathe deeply, twice. If you don't feel anything there,
it's safe for you to talk, as loud as you please."

"I don't feel anything, Conway!" she rejoiced. Tears forgotten, she was
her old, buoyant self again. "So that wall _is_ real, after all? I only
about half believed it."

"Don't trust it too much, because he can cut it off from the outside any
time he wants to. Remember what I told you: that necklace will warn you
of any spy-ray in the ether, and the watch will detect anything below
the level of the ether. It's dead now, of course, since our three phones
are direct-connected; I'm in touch with Bradley, too. Don't be too
scared; we've got a lot better chance than I thought we had."

"What? You don't mean it!"

"Absolutely. I'm beginning to think that maybe we've got something he
doesn't know exists--our ultra-wave. Of course I wasn't surprised when
his searchers failed to find our instruments, but it never occurred to
me that I might have a clear field to use them in! I can't quite believe
it yet, but I haven't been able to find any indication that he can even
detect the bands we are using. I'm going to look around over there with
my spy-ray ... I'm looking at you now--feel it?"

"Yes, the watch feels that way, now."

"Fine! Not a sign of interference over here, either. I can't find a
trace