s, above us in
the tower, must surely be the signal room. Would Brotow follow us up?
I hoped not. I wanted to be alone with the duty-man up there, giving
me a chance to get at the projector controls if Miko's signal should
come.

I drew Anita past Brotow, who had stood aside. "Thanks," I repeated.
"We won't be long."

We mounted the little ladder.

CHAPTER XXXI

_In the Tower Cubby_

"Hurry, Anita!"

I feared that Potan might come up from the hull at any moment and stop
us. The duty-man over us gazed down, his huge head and shoulders
blocking the small signal room window. Brotow called up in Martian,
telling him to let us come. He scowled, but when we reached the trap
in the room floor-grid, we found him standing aside to admit us.

I flung a swift glance around. It was a metallic cubby, not much over
fifteen feet square, with an eight-foot arched ceiling. There were
instrument panels. The range-finder for the giant projector was here;
its little telescope with the trajectory apparatus and the firing
switch were unmistakable. And the signalling apparatus was here! Not a
Martian set, but a fully powerful Botz ultra-violet helio sender with
its attendant receiving mirrors. The _Planetara_ had used the Botz
system, so I was thoroughly familiar with it. I saw, too, what seemed
to be weapons: a row of small fragile glass globes, hanging on clips
along the wall--bombs, each the size of a man's fist. And a broad belt
with bombs in its padded compartments.

My heart was pounding as my first quick glance took in these details.
I saw also that the room had four small oval window openings. They
were breast-high above the floor; from the deck below I knew that the
angle of vision was such that the men down there could not see into
this room except to glimpse its upper portion near the ceiling. And
the helio set was banked on a low table near the floor.

In a corner of the room a small ladder led through a ceiling trap to
the cubby roof. This upper trap was open. Four feet above the
room-roof was the arch of the dome, with the entrance to the upper
exit-lock directly above us. The weapons and the belt of bombs were
near this ascending ladder, evidently placed here as equipment for use
from the top of the dome.

* * * * *

I turned to the solitary duty-man. I must gain his confidence at once.
Anita had laid her helmet aside. She spoke first.

"We were with Set Miko," she said smilingl