"Even so." Hummingbird raised his hand in front of her face. "But your mind was hiding the true world from your consciousness. Look at my hand tonight and you see every single bump and groove in my glove, you see the fire of my bodily electrical field, you see each pore in my skin. But yesterday? Yesterday you saw an idea of a gloved hand. An abstraction. A great part of human mental activity is devoted to reducing this raw flood of images and smells and sensations to remembered symbols. A hand. A man. A dog. An ultralight."

He swung his hand, indicating everything within sight. "Those symbols are not real, but they are very convenient. They let the lazy mind operate in such a confusing world." Gretchen could hear a grin in the man's voice. "Have you seen a baby watching the world? Their eyes are so wide! Their entire mentation is focused upon trying to understand everything all at once. A baby becomes a child and then an adult by replacing raw truth with layers of abstraction. By learning speech. By learning to read and to write. All those tools – the tools which build Imperial society and our science and our technology – hide the true world behind symbols."

"I…I understand." Gretchen felt faint and swayed. Clumsily, she sat down on the sand. The sensation of touching the earth, the sound of sand shifting under her hands, was nearly overwhelming. "What do I do…to be able to, say, move around?"

"Your body can handle everything," Hummingbird said wryly. "If you let it remember. Come, stand up. Let's go for a walk."

Nearly an hour later, Gretchen climbed gingerly across a slab of wind-polished stone and came to a halt, staring down into a wide bowl-shaped depression. To her right, a black lightless cliff rose up into the night. The bowl below her was strangely smooth.

"Where are we?" Anderssen slid down a splintered section of rock and came to a halt a handspan from the surface of the bowl. "This is hard-packed dust," she said, looking up at Hummingbird, who crouched atop the slab. "Not even sand."

The old Mйxica pointed to the cliff. Gretchen turned and saw – suddenly, as if the opening had materialized from the rock in her single moment of inattention – a door. She stiffened, feeling the freezing cold keenly through the insulated layers of her z-suit.

"This is where Russovsky found the cylinder." Hummingbird spoke very softly, though the trapezoidal opening in the cliff-face was entirely dark and still. "Do you see anything?"

Gretchen felt the cold settle into her bones and the pit of her stomach. Learning how to walk again had been easy – just a matter of keeping her mind occupied elsewhere. The body remembered how to breathe, how to walk, how to keep its balance – as long as the mind didn't try to interfere. Talking to Hummingbird about nothing of any importance had let her mind settle and regain its footing in simple physicality. The encompassing darkness restricted her vision to faint thready ghosts of heat and electricity. In time even they seemed to dim and fade as she got used to them. The nauallis claimed she could focus now, once her mind adapted, to bring clarity to bear on a single object.

"Go on," he said, remaining atop the slab. "Let yourself see."

Gretchen sucked on her water tube, eyes closed, feeling her heartbeat speed up. Then she opened her eyes again and looked at the doorway.

"Nothing unusual," she said after a moment. "Worked stone. I don't see any lights inside. Should I?"

"I don't know." Hummingbird made his way down into the bowl. "I came here last night and watched for a time. There were no lights, no blue glow. But I feel uneasy. Everything here is so old…worn down by time. Such places are dangerous, being all of a single cloth. Differences," he said, "are easier to perceive."

"Are we going to go in?" Gretchen still felt cold and a nagging thought was beginning to curdle in the back of her thoughts.

"Yes." Hummingbird looked to her and then back to the doorway. "We have to see if Russovsky left anything behind in there."

Gretchen put a hand on his shoulder as the Mйxica moved to cross the bowl. "This is probably where she was replaced," she whispered, holding him back. "Her flight log shows she headed straight back to the observatory camp from here."

"I know." Hummingbird's hand clasped hers for a moment, fire mingling with fire. "This would mean her remains are within. And those we must destroy."

"Do you still have your little pistol?" Gretchen was digging in her tool belt.

Hummingbird nodded, patting his side. "It's not much use for eliminating evidence."

"Or for dealing with Ephesian lifeforms." Gretchen produced a compact lightwand. She adjusted a thumb control. "This is set to high UV," she said, handing over the lamp. "Everything else seems susceptible; maybe whatever is in there will be too."

The nauallis took the lamp with a shake of his head. "If there's something in there which can duplicate a human being almost to the cellular level, I fear it won't be affected by this."

"Then we need something bigger," Gretchen said, kneeling on the sand. Busy hands detached a variety of tools from her belt and began assembling them. Without looking up, she said: "Bandao-tzin felt he couldn't let me leave his company without proper equipment, so he sent this with me."

She held up a short-barreled, stockless gun with a hand grip and a fat magazine. Hummingbird grunted in appreciation and held out his hand.

"I don't think so," Gretchen said tartly, tucking the assault rifle under her arm. "You're going in first and I'll cover you."

"What does it shoot?" Hummingbird's appreciative smile vanished. He was eyeing the rifle warily now. "It looks like something the Marines would use."

Gretchen shook her head with a smirk. "No – it's Swedish. A Bofors Sif-52 shockgun. Throws explosive flechettes in a room-sized cloud." She locked the magazine back into place. A green light gleamed at the back of the weapon. "So I'll probably wait until you're out of the way."

"Of course." The nauallis did not seem convinced, but he turned away and glided across the hard-packed dust towards the door. Gretchen scuttled along behind him, keeping to his right, the gun leveled on the opening. When he'd reached the edge of the door, she stopped, steadying herself. The barrel of the weapon was a distraction – flickering with curlicues of orange flame – and she concentrated, remembering only smooth, dark solid metal.

Hey, she thought as Hummingbird stepped around the corner into the opening, it works!

The rifle was solid again, barrel heavy and entirely lacking in radiant light.

Gretchen scampered up to the door and peered inside. Hummingbird had tuned the lightwand down low, but the flare of ultraviolet made the chamber entirely visible once Anderssen's goggles kicked in. She saw a large, rocky space with a rumpled, irregular floor. The far wall was not that of a cave, however, but worked stone – much like the frame of the opening she was crouched against – holding a second trapezoidal door.

There was nothing in the chamber save Hummingbird, who was crouched only a meter or two away, the lightwand held out at a stiff angle. Gretchen scanned the rest of the room over the sights of her shockgun, then fixed her attention on the dark space within the second door. There's something odd about all this…she started to think and then her mind sort of froze up like a water pipe caught in the first chill snap of winter in the high timber. Oh, blessed mother! O divine sister of Tepeyac!

Unaware of the fear choking the words in Gretchen's throat, Hummingbird advanced into the chamber, keeping to the left-hand wall. He led with the wand, now burning purplish-blue in high UV setting, and crouched against the flat, smooth wall on the opposite side. Something had caught his eye and the nauallis leaned close to examine some kind of a spot on the wall.