end to protect him from ultra-beam observation.
Therefore he crouched tensely behind a buttress, staring through his
spy-ray goggles, waiting for a moment when none of the Nevians would be
near the entrance, but grimly resolved to act instantly should he feel
any touch of a spying ultra-beam.

"Here's where the pinch comes," he growled to himself. "I know the
combination, but if they're suspicious enough and act quick enough they
can seal that door on me before I can get it open, and then rub me out
like a blot; but ... ah!"

The moment had arrived, before the touch of any revealing ray. He
trained the key-tube, the entrance opened, and through that opening in
the instant of its appearance there shot a brittle bulb of glass, whose
breaking meant death. It crashed into fragments against a metallic wall
and Costigan, entering the vessel, consigned its erstwhile crew one by
one to the already crowded waters of the lagoon. He then leaped to the
controls and drove the captured speedster through the air, to plunge it
down upon the surface of the lagoon beside the door of the isolated
structure which had for so long been his prison. Carefully he
transferred to the vessel the motley assortment of containers of
Vee-Two, and after a quick check-up to make sure that he had overlooked
nothing, he shot his craft straight up into the air. Then only did he
close his ultra-wave circuits and speak.

"Clio, Bradley--I got away clean, without a bit of trouble. Now I'm
coming after you, Clio."

"Oh, it's wonderful that you got away, Conway!" the girl exclaimed. "But
hadn't you better get Captain Bradley first? Then, if anything should
happen, he would be of some use, while I...."

"I'll knock him into an outside loop if he does!" the captain snorted,
and Costigan went on:

"You won't need to. You come first, Clio, of course. But you're too far
away for me to see you with my spy, and I don't want to use the
high-powered beam of this boat for fear of detection; so you'd better
keep on talking, so that I can trace you."

"That's one thing I _am_ good at!" Clio laughed in sheer relief. "If
talking were music, I'd be a full brass band!" and she kept up a flow of
inconsequential chatter, until Costigan told her that it was no longer
necessary; that he had established the line.

"Any excitement around there yet?" he asked her then.

"Nothing unusual that I can see," she replied. "Why? Should there be
some?"

"I hope not, but when I m