he Ragged Men.... Poison gas.... It'll kill
Denham and Evelyn.... He wants me to do something...."

He drew back, staring, straining every nerve to think.... And somehow
his eyes were drawn to the back of the laboratory and he saw Smithers
teetering on his feet, with his hands clasped queerly to his body, and
a strange man standing in the door of the laboratory with an automatic
pistol in his hand. The automatic had a silencer on it, and its
clicking had been drowned out, anyhow, by the roaring of the crude-oil
engine.

The man was small and dark and natty. His lips were drawn back in a
peculiar mirthless grin as Smithers teetered stupidly back and forth
and then fell....

The explosion of Tommy's own revolver astounded him as much as it did
Jacaro's gunman. He did not ever remember drawing it or aiming. The
natty little gunman was blotted out by a spouting mass of white
smoke--and suddenly Tommy knew what it was that Denham wanted him to
do.

* * * * *

There was rope in a loose and untidy coil beneath a work bench. Tommy
sprang to it in a queer, nightmarish activity. He knew what was
happening, of course. Von Holtz had seen the magnetic catapult at
work. That couldn't be destroyed or its workings hidden like the ring
catapult of Denham's design. He'd gone out to call in Jacaro's men.
And they'd shot down Smithers as a cold-blooded preliminary to the
seizure of the instrument Jacaro wanted.

It was necessary to defend the laboratory. But Tommy could not spare
the time. That white mist was moving upon Evelyn and her father, in
that other world. It was death, as the terror of the wild things
demonstrated. They had to be helped....

He knotted the rope to the end of the cord that vanished curiously
somewhere among the useless mass of rings. He tugged at the cord--and
it was tugged in return. Denham, in another world, had felt his signal
and had replied to it....

A window smashed suddenly and a bullet missed Tommy's neck by inches.
He fired at that window, and absorbedly guided the knot of the rope
past its vanishing point. The knot ceased to exist and the rope crept
onward--and suddenly moved more and more swiftly to a place where
abruptly it was not. For the length of half an inch, the rope hurt the
eyes that looked at it. Beyond that it was not possible to see it at
all.

Tommy leaped up. He plunged ahead of two separate spurts of shots from
two separate windows. The shots pi