"Who are they?" Foss asked.

"Lidj—the Patrol officer—there and there!" He faced the outer transparent wall of the room, pointed right and left to those other two aliens on display. "I saw them—saw them being brought in, forced to exchange. Just as was done with me!"

"I wonder why such exchanges are necessary," Thanel said. "If we could restore this body, why didn't they just restore their own? Why go through the business of taking over others?"

Griss was rubbing his forehead with one hand. "Sometimes—sometimes I know things—things they knew. I think they value their bodies too highly to risk them."

"Part of their treasures!" Foss laughed harshly. "Use someone else to do their work for them, making sure they have a body to return to if that substitute suffers any harm. They're as cold-blooded as harpy night demons! Well, let's see if we can get Lidj and that man of yours out of pawn now."

Borton leaned over the edge of the chair, reaching for the crown Griss had thrown there.

"No!" In a stride Griss closed the distance between them, sent the crown spinning across the floor. "In some way that is a com, giving them knowledge of what happens to the body—"

"Then, with your breaking that tie," I pointed out, "they—or he—will be suspicious and come looking—"

"Better that than have him force me under control again without my knowing when that might happen!" Griss retorted.

If the danger he seemed to believe in did exist, he was right. And we might have very little time.

Borton spoke first. "All the more reason to try to get the others free."

"Which one is Lidj?" Foss was already going.

"To the left."

That meant the bird-headed crown. We returned to the anteroom. Griss threw open one of the chests as if he knew exactly what he was looking for. He dragged out a folded bundle and shook it out, to pull on over his bare body a tightly fitting suit of dull black. It was all of a piece including footgear, even gloves, rolled back now about the wrists, and a hood which hung loose between the shoulders. A press of finger tip sealed openings, leaving no sign they had ever existed.

There was something odd about that garment. The dull black seemed to produce a visual fuzziness, so that only his head and bared hands were well-defined. It must have been an optical illusion, but I believed that with the gloves and hood on he might be difficult to see.

"How did you know where to find that?" Borton was watching him closely.

Griss, who had been sealing the last opening of his clothing, stopped, his finger tip still resting on the seam. There was a shadow of surprise on his handsome face.

"I don't know—I just knew that it was there and I must wear it."

Among them all, I understood. This was the old phenomenon of shape-changing—the residue (hopefully the very small residue) of the earlier personality taking over for some actions. But there was danger in that residue. I wondered if Griss knew that, or if we would have to watch him ourselves lest he revert to the alien in some more meaningful way.

Thanel must have been thinking along the same lines, for now he demanded: "How much do you remember of alien ways?"

Griss's surprise was tinged with uneasiness.

"Nothing! I was not even thinking—just that I needed clothing. Then I knew where to find it. It– I just knew—that's all!"

"How much else would he 'just know,' I wonder?" Borton looked to Thanel rather than to Griss, as if he expected a better explanation from the medic.

"Wasting time!" Foss stood by the door. "We have to get Lidj and Harkon! And get out before anyone comes to see what happened to Griss."

"What about my cap?" I asked.

Thanel had passed that to the other Patrolman. And in this place I wanted all the protection I could get. The other held it out to me and I settled it on my head with a sigh of relief, though with it came the sensation of an oppressive burden.

We threaded along that very narrow passage to the next chamber, where the alien with the avian crown half-reclined on the couch. Having freed one "exchange" prisoner, I now moved with confidence. And it was not so difficult, as Juhel Lidj had greater esper power.

Then we retraced our way and released Harkon also. But I do not believe that Borton was entirely happy over such additions to our small force. They had put aside their crowns, and they were manifestly eager to move against those who had taken their bodies. But whether they would stand firm during a confrontation, we could not know.

.We returned to the cat door. There I lingered a moment, studying the mask symbol. Three men, one woman—who had they been? Rulers; priests and a priestess; scientists of another time and place? Why had they been left here? Was this a depository like our medical freezers, or a politically motivated safe-keep where rulers had chosen to wait out some revolution they had good reason to fear? Or—

It seemed to me that the gem eyes of the cat held a malicious glitter, mirroring superior amusement. As if someone knew exactly the extent of my ignorance and dismissed me from serious consideration because of it. A spark of anger flared deep inside me. Yet I did not underrate what lay beyond that door and could be only waiting for a chance to assume power.

"Now where?" Borton glanced about as if he expected some guide sign to flare into life.

"Our other men," Lidj answered that crisply. "They have them imprisoned somewhere—"

I thought that "somewhere" within these burrows was no guide at all. And it would seem Foss's thoughts marched with mine, for he asked:

"You have no idea where?"

It was Harkon who answered. "Not where they are. Where our bodies are now, that is something else."

"You mean you can trace those?" Thanel demanded.

"Yes. Though whether mere confrontation will bring about another exchange—"

"How do you know?" The medic pursued the first part of his answer.

"I can't tell you. Frankly, I don't know. But I do know that whoever is walking about as Harkon right now is in that direction." There was no hesitation as he pointed to the right wall of the passage.

Only, not being able to ooze through solid rock, I did not see how that knowledge was going to benefit us. We had found no other passage during our way in (I was still deeply puzzled about the difference between my first venture into the maze and this one).

Harkon still faced that blank wall, a frown on his face. He stared so intently at the smoothed stone that one might well think he saw a pattern there—one invisible to us.

After a moment he shook his head. "Not quite here —farther on," he muttered. Nor did he enlarge on that, but started along close to the wall, now and then sweeping his finger tips across it, as if by touch he might locate what he could not find by sight. He was so intent upon that search that his concentration drew us along, though I did not expect any results from his quest. Then he halted, brought the palm of his hand against the stone in a hard slap.

"Right behind here—if we can break through."

"Stand aside." Whether Borton accepted him as a guide or not, the commander seemed willing to put it to the test. He aimed his weapon at the wall where Harkon had indicated, and fired.

The force of that weapon was awesome, more so perhaps because we were in such a confined space.

One moment there had been the solid rock of this planet's bone; the next—a dark hole. Before we could stop him, Harkon was into that.

We had indeed broken through into another corridor. This one was washed in gray light. Harkon did not hesitate, but moved along with such swift strides that we had to hurry to catch up.

That passage was short, for we soon came out on a gallery running along near the top of another pyramid-shaped chamber. This one was triple the size of the others I had seen. From our perch we looked down into a scene of clanking activity. There was a mass of machinery, installations of some sort, being ,uncrated, unboxed by robos. Pieces were lifted by raise cranes, transferred to transports. But those carriers ran neither on wheels nor—