be
turned loose. But the woman--those yellow men....

Martin's ears became suddenly aware of a faint, strange sound. It was
a sound he had been endeavoring subconsciously to place during the
period of his musing; he had almost identified it as his heart-beats.
Now, alert and listening, he placed it. It was a tapping on the other
side of the wall he leaned against, a light tap-tap-tap. It started,
stopped, started.

Somebody was tapping on the wall in the next room. Another prisoner!
It was the girl--of course, it was the girl.

Martin was instantly sure of the tapper's identity, with a sureness
born of intuition and memory. He remembered the two doors opening from
the big room, the gray overcoat lying in the corner, Carew's words when
the semi-conscious Martin Blake was held poised before the other door.
"Not there--next room." Those were Carew's words. Why, of course, the
Japs had brought the girl to Carew, and he had shut her in the next
room.

_Tap-tap-tap, tap-tap_. There it came again. Martin rapped against
the wall with his own knuckles, paused, rapped again. Instantly came
the response from the other side, the same number of raps. A plain
answer.

But Martin's elation was short lived. The unseen tapper immediately
commenced again, _tap-tap, tap-tap-tap-tap, tap_.

Surely there was method in that irregular tapping. A signal, a talk in
code! But he could not read it. Nor dare he lift his voice in shouted
communication through the wall--Spulvedo, and bullets, hung over him.
One experience of being shot at while unarmed and helpless was
sufficient. It would not help the girl for him to get himself shot.

The unevenly tapped message came again. The best he could do was
repeat the taps. But this, evidently, did not satisfy the sender. The
tapping on the other side ceased. Though he rapped till his knuckles
were sore, he could not induce the other to recommence.

The gloom of the room was less dense, Martin's accustomed eyes being
now able to discern all four walls and the outline of the window.
A-fever with excitement as he was, the inactivity palled upon him,
became unbearable. He must do something. Well, he would try the
window again.

But first he crept to the door and endeavored to peer through the
key-hole into the big room. He hoped to get a view of what was
happening without, of Carew, of Spulvedo. But he was disappointed.
The key, thrust in the lock on the outer side, compl