"There are two main port-locks in the dome for space-ships, and the starboard one has a smaller man-size lock beside it. We're going to the smaller one. There'll no doubt be a guard on watch at it, so to him we're Ku Sui and the two men who accompanied him. We'll have to chance recognition; but at least there's no difference in the suits we're wearing, and we'll clasp our glasses on all the way to the lock, for surely Dr. Ku has to use some similar device. Keep your faces averted as much as you can though, when near, and your rayguns in your belts. If there's to be gunplay, leave the first shot to me. You'll both follow me just as those two followed Dr. Ku."

Ban Wilson asked: "Will you go down into the valley between the trees, then up the face of the rock? The guard wouldn't see us until we were right at the lock."

"No, he wouldn't: but he'd wonder why Ku Sui was being so cautious. We'll go straight across, in full view. We'll get in easily, or—well, that depends. Ready?"

They fastened the glasses over their eyes, keeping the helmet face-plates partly open. The rayguns they eased in their belt holsters, and slid back the hinged palms of their mittens, to give exit if need be to their gun-hands. They were ready.

Switching on the helmet gravity-plates to swift repulsion, the three soared out of the trees, soared up on a straight, inclined line for the dome on the asteroid, a steady, rapid climb that soon raised them one mile, a second and a third, where they leveled off and sped straight ahead. Now they could look right into the dome.

Rapidly the port-lock that was their objective grew in size. Behind it were the buildings: the large, four-winged central structure and the supplementary workshops and hangars, coolie-quarters and outhouses, all dim and shimmering through the infra-red—the mysterious, lonely citadel of Dr. Ku Sui. There it all was, inside the dome, with the rest of the asteroid looming massive behind.

A quarter-mile away, and swiftly half that, and half again the three grouped figures arrowed ahead without hesitation. And the Hawk said curtly:

"I see no men—do either of you? It looks deserted."

"There!" cried Ban, after a second. "There! Beside the port-lock. Just now!"