Stephen had come to his senses while the professor was speaking. The man was staring
steadily at the ominous figure of The Shadow. He trembled when he heard the sinister tone
of the voice that replied to Professor Whitburn.
'Have no fear for Dadren,' declared The Shadow, in a tone that bore a tinge of mockery. 'I
made arrangements for his welfare, immediately after the call from you. He will be warned of
danger.'
WITH that, The Shadow turned and began to inspect the submarine chamber. He stopped
by the machine on which Quex was curled. The cat blinked and turned away from The
Shadow's burning eyes. A soft laugh whispered from unseen lips.
The Shadow remembered this submarine room. Once he had rescued his agent, Harry
Vincent, from imprisonment within these very walls. Deep beneath the house, this room was
below the level of the lake. It fronted on a subterranean channel under the island.
Professor Whitburn had used it for torpedo tests. At the time of Harry Vincent's
imprisonment, the torpedo tubes had been in use. A girl—Arlette Deland—had been a
prisoner with Harry; and the agent, at The Shadow's command, had sped the girl to safety
within a torpedo.
But none of these contrivances were usable at present. Machinery dismantled, torpedoes
gone, the room was but a relic of Whitburn's former experiments. Just above the machine on
which Quex rested was a periscope that formed a solid shaft up through the top of the room.
This led above ground, and the professor had used it to watch the progress of his
torpedoes.
At the time of Harry's imprisonment, there had been water sluices in the submarine
chamber. These had been installed in order to flood the room in case spies tried to enter.
No longer needed, the sluices had been blocked.
But the locked door still remained. The Shadow had opened it once from the outside. The
inner wall, however, offered a most difficult task—one that would take hours, at least. By
morning—before the barrier could be cut—life could no longer exist in this cramped space.
Moreover, Bragg, returning and departing, would be on the way to Eric Hildrow's toils.
Yet The Shadow approached the door. He studied its smooth, riveted surface. He saw that
with few tools available, this means of exit afforded slow progress. With him, The Shadow
had another means of attacking the door. Two powders, mixed, would form a high explosive
that might blast the barrier from its hinges.
Here, again, was danger. The steel door was unusually formidable. Should a first blast fail,
as was highly probable, the fumes would exhaust the remaining air supply. That would
hasten death instead of prolonging life.
WHILE The Shadow was examining the door, Quex rose from his perch. In placid fashion,
the big cat dropped from the machine and stalked over to the stone steps. Ascending, Quex
began to claw at the fringe of The Shadow's cloak.
Lowering his gaze, The Shadow looked at the cat. Quex moved to the door and showed the
claws of one paw as he scratched inquiringly at the steel barrier. The Shadow laughed
softly; then turned toward Professor Whitburn.
'Quex always does that,' explained the white-haired inventor. 'If he is locked out at night, he
claws at the front door until I open it.'
The cat began to mew.
'That follows,' added the professor. 'Then, if no one answers, he sits by the door. He waits
until he is admitted. Twice, when I was away all night, I returned to find him waiting for me.'
The Shadow made no response. Yet his steady gaze impelled the professor to a further
statement.
'If that fiend had left Quex in the study,' declared Whitburn, 'Bragg would have known that
something was wrong. When he returns to-morrow, you understand.'
'And if the cat had been taken from the house,' whispered The Shadow, 'then -'
'Quex would come back to the front door,' completed Whitburn, 'to wait there for the first
person who might arrive. If he could only be where Bragg could find him -'
Whitburn shook his head as he speculated. He watched The Shadow come away from the
door. He saw the cloaked rescuer stop at the periscope above the machine.
The periscope consisted of a lower reflector, connected with another mirror above the
ground. Between the two were lenses. Only the lower reflector was visible; the rest of the
apparatus was encased in the tube that led up through the low ceiling of the room.
The Shadow studied the periscope. Whitburn thought that he was trying to sight through it.
The professor could see no purpose in such action, for nothing could be gained by staring
out into the blackness above ground.
As Whitburn watched, however, he suddenly realized The Shadow's purpose. The
periscope was patterned after those used in undersea boats; its construction, though, was
of the most simple sort, for it had no water to encounter. The encasing tube merely protected
the apparatus; and it was firmly fixed in position.
That tube had given The Shadow a solution to the problem of failing air. With gloved hands,
he began to detach the lower reflector. That done, he worked to remove the lenses and
other connections from within the tube itself.
PROFESSOR WHITBURN chortled. The Shadow was forming an air shaft to the clear
atmosphere above. Emptied of its equipment, the periscope tube formed a tunnel six inches
in diameter, leading straight upward. Only one problem remained. That was the upper
reflector.
Sudden dismay gripped Whitburn as he saw The Shadow blink a flashlight up through the
tube.
'The upper reflector is encased,' exclaimed the professor. 'It is larger than the tube. It is
screwed in place. Even if you break its bottom lens, you can not obtain air. There is an outer
glass, off at an angle -'
He shook his head as he paused. The Shadow was unscrewing a long bar from the
machine beside the old torpedo tube. With it, he could attack the lower lens of the upper
reflector; but as Whitburn had said, it would be impossible to curve this bar and reach the
outer glass.
The Shadow, however, had another plan. From beneath his cloak, he drew forth an odd
device. It was a rubber suction cup—one of those which The Shadow used to scale vertical
walls. The rubber disk was just a trifle smaller than the periscope tube.
Laughing softly, The Shadow used a clamp to fit the disk to the end of the steel bar.
He thrust the disked end of the bar straight up the periscope tube. Whitburn could hear the
squdge of the rubber sucker as it pressed against the lower lens at the top of the tube. Then
he began to revolve the bar. The professor gaped.
The suction cup had gained a grip. By twisting the bar, The Shadow was unscrewing the
mushroom cap that covered the upper end of the periscope tube. After a few moments, The
Shadow thrust the bar upward. A puff of air came down the shaft.
Jerking at the bar, The Shadow managed to detach the suction cup. Professor Whitburn
could hear the loosened cap rattle away from the top of the tube. The submarine chamber
was no longer a death trap. The prisoners could remain here indefinitely, with no danger of
suffocation.
Yet this passage to the outer air afforded no means of escape. Professor Whitburn
wondered what would follow. There would be no chance of communication with Bragg when
