e crack of the
door, he stood bracing it.

A furious pounding shook the door. A heavy pressure bent it inward.

"Quick!" the big black gasped. "Somethin' to wedge it!"

"A minute, Friday," the Hawk answered. "Hold it!"

He was already dragging a metal table there; and, upended under the
knob, making an angle with the floor, it held stoutly closed the door,
now thumping and quivering with blows given it from outside. The panting
negro fell back from the door exhausted, but rose to help his master at
the need for placing additional barricades.

That finished, the Hawk wheeled, and at once, pantherlike, ray-guns at
the ready, stalked the room. There was no sign of the enemy. He
approached the operating table.

A great relief flooded his grim face as he sighted Eliot Leithgow lying
there, apparently untouched and still conscious. The elderly scientist
was strapped down tight, but he was smiling.

"I knew you'd come, Carse, if you could," he said simply.

There was no time for visiting. "Where's Ku Sui?" the adventurer asked.

"Gone," Leithgow answered. "I heard a door open and close--which one I
couldn't see. He went as soon as that bell began to ring. The
assistants, too."

Through the shouts and batterings at the barricaded door came a new
sound--from another direction. Like a streak the Hawk was at one of the
three other doors, throwing its inside hand bolt; and by the time he had
shot over the second, Friday had taken the cue and secured the remaining
one.

The negro let out a vast breath. "Umph!" he said. "I'll tell the
universe that was close!"

* * * * *

Hawk Carse said nothing. With eyes ever-watchful for sign of a trick or
a trap in the apparently deserted laboratory, he quickly unbuckled the
bands that held Leithgow to the operating table. Friday lifted the
scientist to the floor, where he stretched weakly.

The adventurer smiled faintly, then his eyes went cold and serious.
Crisply he said:

"We came, yes--but now I think we're trapped. There'll be men outside
each of these four doors. The bolts may hold them a while, but
eventually they'll get through. We must look for further weapons. If
only there were better light! Friday," he ordered, "look for a switch.
_Ah!_"

With a thud and a booming reverberation a systematic battering had begun
on the metal door through which they had entered. It quivered visibly
and rang as the powerful blows from the othe