t they lay stunned by a realization that their escape was
blocked.

"Kiss me good-by, dear," breathed Milli. "This is the end."

As the young man reached over to take her in his arms, the submarine
was suddenly lifted up and spun backward, end over end: then tumbled
and bumped along, as though it were a chip on an angry mountain
torrent.

Stunned and bruised and bleeding, the young American finally lost
consciousness....

* * * * *

When he came to his senses again, his first words were, "Milli, where
are you?"

"My darling!" breathed a voice at his side. "Are you all right?"

"Yes," he replied. "Where are we? What has happened?"

"The entire system of locks must have crashed in and flooded the
city," said she.

Instantly Abbott's mind grasped the explanation of this occurrence:
their leaving open so many gates behind them had made it impossible
for the few remaining gates ahead to withstand the terrific pressures
of the ocean depths, and they had crumpled. But he did not tell Milli
his part in this.

She continued, "I was pretty badly shaken up myself, but I've got this
boat going again, and we're on our way out of the tunnel. See--I've
found out how to work our searchlight."

He looked. A broad beam of light from their bow, illuminated the
tunnel ahead of them.

Presently another beam appeared, shooting by them from behind.

"Hakin and Romehl!" exclaimed the girl. "Then they're safe, too!"

The tunnel walls grew rough, then disappeared. They were out in the
open sea at last, although still one mile beneath the surface.

But in front of them was an angry seething school of the man-sharks,
clearly illumined by the two rays of light. Behind the sharks were a
score or more of serpentine steeds.

The sharks saw the two submarines and charged down upon them; but
Milli, with great presence of mind, shut off her searchlight and swung
sharply to the left.

"Up! Up!" urged the young man, so she turned the craft upward.

* * * * *

On and on they went, with no interference. Presently they turned the
light on again, so as to see what progress they were making. But they
were making absolutely none! They were merely standing on their tail.
They had reached a height of such relatively low pressure that it took
all the churning of their propeller just merely to counteract the
great weight of their submarine.

Abbot switched on their chemical gas