looked in.

"The ober-lieutenant sends his compliments," announced the fellow, in
English. "He will be pleased to have you join him. I will lead the way."

Dave followed, down the passage and out into the main cabin. There, at a
table under the conning tower, sat the ober-lieutenant and the same
younger officer.

"We will raise the periscope and show you what we are about to do," said
the ober-lieutenant, with a half-malicious smile.

Von Schellen, his hand on the wheel of the periscope mechanism, awaited a
nod from his chief. Receiving it, the younger officer turned the wheel,
sending the periscope up a foot above water.

On the white surface of the shaded table beneath Dave saw the image of a
vessel.

"The fellow yonder has not yet sighted us," said the ober-lieutenant,
grimly. "We are about to send him a torpedo. Yonder craft is to be our
game--Yankee steel and Yankee meat!"

As for Dave, as he stared in horror at the image on the table he
recognized in the ship mirrored there Dan Dalzell's own command, the
"Reed."

Forcing himself to speak calmly, and to act a part Dave begged:

"One moment longer, please! Let me see whether I can recognize the doomed
craft."

"Doomed, indeed," chuckled the ober-lieutenant. "We are in position and I
am about to fire. Be ready to drop the 'scope, von Schellen!"

But Dave Darrin, knocking von Schellen's hand away, seized the lever,
forcing the periscope to rise to its full height above the conning tower.
Nor did he stop there. With the mightiest twist and wrench of which he
was capable he jammed the lever so that it could not be promptly operated
to lower the periscope.

"Stop!" thundered von Schellen, leaping to his feet, his face purple with
rage.

"I've stopped," assented Darry, smilingly, as he stepped back.

"Do you realize what you have done, scoundrelly Yankee?" hissed the
ober-lieutenant, also rising and drawing his revolver.

"Of course I do," Dave smilingly assented.

"You have jammed the periscope. But at least we can dive when we need,
for--there!"

With deft manipulation of a small device the German commander added:

"I have closed the valves of the 'scope, which will now admit no water if
we dive. You did not succeed, Herr Darrin. But you will draw upon us the
Yankee fire if yonder commander is now able to sight our scope."

As if to verify the statement a muffled sound came to them through the
water. Glancing down swiftly at the table von Schelle