stood for a moment
motionless, speechless. Then, as one, Larry and the professor rushed
forward and beat upon that barred hatch, calling upon Von Ullrich to
open it.

From within the submarine, through their vibrators, they heard him
laugh.

"_Auf Wiedersehen!_" he toasted them. "I now have all the treasure I
want! The rest I leave to you! Help yourselves!"

Even as he spoke, the _Nereid's_ auxiliary propellers started churning
the water. Slowly, sluggishly, like some great gorged fish, the sturdy
craft moved off, lifted her snout, headed upward.

* * * * *

Professor Stevens bowed his head, and Larry could well picture the
grief that distorted the graybeard's face, inside that owl-eyed
helmet.

"Cheer up!" he said, though his own face was twisted with anguish.
"Perhaps--"

Then he paused--for how could he say that perhaps the situation wasn't
as bad as it seemed, when it was obviously hopeless?

"My poor Diane!" moaned the professor. "Poor child. Poor child!"

As for Captain Petersen and the crew, they said nothing. Perhaps they
were thinking of Diane, perhaps of themselves. At least, they knew it
was over.

Or so they thought. But to Larry, suddenly, occurred a gleam of hope.
That strange sense of unseen presences! It was bizarre, of course, but
doesn't a drowning person catch at straws? And Lord knows they were
drowning, if ever anyone was!

He turned and confided to Professor Stevens his idea, which was to
retrace their steps within the city gates, seek out the populace and
throw themselves on their mercy.

The stricken savant, too, grasped at the straw.

"It seems fantastic, but after all it is a chance," he admitted.

So they pushed back into that great submerged city, with Captain
Petersen and his skeptical crew. They entered one of the largest of
the temples, wandered forlornly through its flooded halls and
corridors, seeking some sign of these alleged beings Larry had sensed.

Nor was their search unrewarded, for suddenly the captain himself,
most skeptical of all, cried out:

"Listen! Did you hear that?"

There was no need to ask the question, for all had heard. It was a
rasping sound, as of some great door swinging shut, followed almost
immediately by a rushing gurgle--and as they stood there tense, the
water level began rapidly receding.

Even while it was still plashing about their ankles, a secret block of
masonry slid back and a horde of Antillians b