tacles. If only the tunnel would
continue right into the original cavern! If only their path would stay
clear and unhindered!

But it did not. The sound of Phil's footsteps ahead stopped, and when
Sue and her father came up they saw why.

"A river!" Phil said.

* * * * *

They were standing on a narrow ledge that overhung an underground
river. A fetid smell of age-old, lifeless water rose from it. Dimly,
at least fifty feet across, they could see the other side, shrouded in
vague shadows. The inky stream beneath did not seem to move at all,
but remained smooth and hard and thick-looking.

They could not go around it. The ledge was only a few feet wide, and
blocked at each side.

"Got to cross!" Phil said tersely.

Quade, sickly-faced, stared down. "There--there might be other things
in that water!" he gasped. "Monsters!"

"Sure," agreed Phil contemptuously. "You'd better stay here." He
turned to the others. "I'll see how deep it is," he said, and without
the faintest hesitation dove flatly in.

Oily ripples washed back, and they saw his head poke through,
sputtering. "Not deep," he said. "Chest-high. Come on."

He reached for Sue, helped her down, and did the same for her father.
Holding each by the hand, Sue's head barely above the water, he
started across. They had not gone more than twenty feet when they
heard Quade, left on the bank, give a hoarse yell of fear and dive
into the water. Their dread pursuer had caught up with them.

And it followed--on the water! Phil had hoped it would not be able to
cross, but once more the thing's astounding adaptability dashed his
hopes. Without hesitation, the whitish jelly sprawled out over the
water, rolling after them with ghastly, snake-like ripples, its pallid
body standing out gruesomely against the black, odorous tide.

Quade came up thrashing madly, some feet to the side of the other
three. He was swimming--and swimming with such strength that he
quickly left them behind. He would be across before they; and that
meant there was a good chance that the earth-borer would go up again
with only one passenger....

Phil fought against the water, pulling Sue and her father forward as
best he could. From behind came the rippling sound of their shapeless
pursuer. "Ten feet more--" Holmes began--then abruptly stopped.

There had been a swish, a ripple upstream. And as their heads turned
they saw the water part and a black head, long, e