ent tubes, we stood holding
our breaths, peering and listening. No one here.

The guard was not dead. He lay unconscious from a blow on the head. A
brawny fellow. We had him revived in a few moments. A broadcast flash
of the call buzz brought Dr. Frank from the chart room.

"What's the matter?"

"Someone was here," I said hastily, "experimenting with the magnetic
switches. Evidently unfamiliar with them--pulling one or another to
test their workings and so see their reactions on the dials."

We told him what had happened to Snap in the corridor; the guard here
was no worse off for the episode, save a lump on the head by an
invisible assailant. We left him nursing his head, sitting belligerent
at his post, alert to any danger and armed now with my heat-ray
cylinder.

"Strange doings this voyage," he told us. "All the crew knows it. I'll
stick it out now, but when we get back home I'm done with this star
travelin'. I belong on the sea anyway."

We hurried back to the upper level. We would indeed have to plan
something at this chart room conference. This was the first tangible
attack our adversaries had made.

We were on the passenger deck headed for the chart room when all three
of us stopped short, frozen with horror. Through the silent passenger
quarters a scream rang out! A girl's shuddering, gasping scream.
Terror in it. Horror. Or a scream of agony. In the silence of the
dully vibrating ship it was utterly horrible.... It lasted an
instant--a single long scream; then was abruptly stilled.

And with blood pounding my temples and rushing like ice through my
veins, I recognized it.

Anita!

IX

"Good God, what was that?" Dr. Frank's face had gone white. Snap stood
like a statue of horror.

The deck here was patched as always, with silver radiance from the
deck ports. The empty deck chairs stood about. The scream was stilled,
but now we heard a commotion inside--the rasp of opening cabin doors;
questions from frightened passengers.

I found my voice. "Anita! Anita Prince!"

"Come on!" shouted Snap. "In her stateroom, A22!" He was dashing for
the lounge archway.

Dr. Frank and I followed. I realized that we passed the deck door and
window of A22. But they were dark, and evidently sealed on the inside.
The dim lounge was in a turmoil; passengers standing at their cabin
doors.

I shouted, "Go back to your rooms! We want order here--keep back!"

We came to the twin doors of A22 and A20. Both w