The stranger's lift closed. Mira watched the reflective panel slide across the figure and carry the silhouette off with it, the way a solvent lifts color out of a stain.
Gideon moved before she did. He set his palm flat against the filter membrane, not pushing, reading. "Count with me."
"Count what."
"Floors."
She listened. The lift's descent came to her as a change in pressure behind her ears, faint, then fainter. Gideon's lips moved without sound. His hand stayed spread against the membrane, and she caught herself watching the tendons flex in the back of it instead of counting. Three years he had hunted her, and she had built him in her head as a voice on the wrong side of a door. Not a man who counted floors under his breath because panic was an expense he declined to pay.
"Forty," he said. "It stopped on forty."
"One below us."
"One below us." He took his hand away. The membrane held the shape of his warmth for a moment, then surrendered it, scrubbed clean.
Mira pressed her own hand to the lift panel where the stranger's gesture had been accepted. Nothing. The tower wanted the joined identity, and it wanted both halves of it present and calm, and one half of her was neither. The panel considered her wrist, considered Gideon three steps back, and only when he came and stood at her shoulder did the compartment agree to open.
"That's the leash," she said. "We move together or we don't move."
"You noticed."
"I notice everything I can't undo."
They did not follow the stranger to forty. Directorate protocol did not permit two confined witnesses to descend on impulse, and by the time the membrane logged their exit the lift below had gone somewhere the record refused to say. Mira memorized that refusal. A log that would not name a floor was a log someone had been permitted to edit.
---
Anika met them at the seam of the security floor with a reader in each hand and her collar askew, as though she had run and then decided running was undignified and slowed to a walk too late.
"Don't talk," she said. "Let me get this out before it stops being interesting." She turned the left reader toward them. A signature bloomed on the display, a lattice of pale lines. "That's you two. That's the tandem marker, the whole executive grid, unique and un-forgeable and all the words in the brochure." She turned the right reader. "That's what opened the door on thirty-nine forty seconds before yours."
Mira looked. The second lattice was the first one drawn by a shaking hand. Most of the lines matched. Some ended early, frayed to nothing. A whole quadrant simply wasn't there.
"Forty-one percent," Anika said. "Give or take. Enough of your grid to satisfy a low-tier door that doesn't ask hard questions. Not enough to satisfy anything on this floor, which is why our friend went down and not up." She looked up, bright and blunt. "Somebody has a copy of you. A bad copy. But a copy."
Gideon went still in the particular way Mira had begun to recognize, the stillness that meant the anger was there and he had decided to spend the moment learning instead. "A copy of a biometric identity," he said. "That's supposed to be impossible."
"So was one identity in two bodies until Tuesday." Anika shrugged. "The tower's tolerance is the problem. It was built to accept degraded reads, sweat and skin and cold fingers, because executives get annoyed when doors don't love them. Feed it enough of a real signature and it fills in the rest with hope. Somebody worked out exactly how little of you they needed."
"When," Gideon said. Narrow question. He had already skipped past the horror to the timeline.
"The murder site," Anika said. "The credential that got accepted while you were leaving. Same signature as this. So the sampling happened before that, or at it. They didn't need much. A door you both touched. A rail. A cup." She grimaced. "I don't love that I can't tell you which."
Mira had gone quiet, and quiet was a thing she was good at, so no one asked her to stop. She was looking at the frayed ends of the second lattice, at the quadrant that was missing, and she was reading it the way she read her own handwriting.
The copy was not merely incomplete. It was decaying. The lines did not end because the sampler had run short of material. They ended because something in the copy was eating itself, retreating a little further each time it was read, a signature designed to unwrite its own edges.
She knew that decay. She had built it. Years ago, in a smaller life, she had folded a self-erasing tag into the lacuna base so that any compound made from her work would slough its own provenance and leave nothing to trace back to a bench. It was elegant. It was hers. And it was sitting in the confiscated research the Directorate had carried out of her laboratory in sealed boxes with Selene Armit's authorization printed on the lids.
Whoever had grown this copy of them had done it with her stolen chemistry. Which meant they had reached the boxes. Which meant they were inside the only walls that were supposed to be keeping her safe, or they had a friend who was.
"What is it," Gideon said.
He was watching her. Not the readers. Her. He had turned his whole attention off the impossible thing in Anika's hands and put it on Mira's face, because he had learned, in two days, that the most dangerous data in any room was the fact she was choosing not to give him.
"It's a poor forgery," Mira said. "Rushed. Whoever made it will need to remake it soon, because it won't hold." All true. None of it the thing.
"How soon."
"Days. The degradation is accelerating." She pointed at the frayed quadrant, at ground she could afford to give. "See how the loss clusters here. That's not random sampling. That's a batch that was never stabilized. They have a source. They don't have the recipe."
Anika made a small delighted sound and started tapping. "Oh, that's good. That's a clock. If it's decaying that fast, they have to come back to whatever they're growing it from, and the tower will see them do it, and I will be watching the tower." She looked up. "You're useful. I hate that I said that out loud."
"Retract it," Mira said. "I'll allow it."
Gideon didn't smile. He was still watching her, and she felt the watching like a temperature. "You said they don't have the recipe," he said. "You'd know the recipe."
"I'd know a hundred recipes."
"I'm asking about this one."
Here was the narrow question arriving at the exact soft place. He had walked to it without hurry, the way he'd counted floors, and she understood, standing there, precisely what made him hard to lie to. He did not accuse. He noticed, and then he waited, and the waiting did the work an accusation couldn't, because there was nothing in it to push against. She wanted, absurdly, to give him something true just to end the silence he was so comfortable inside.
She gave him a different truth instead.
"If I built a copy of us," she said, "I'd stabilize it with the same precursor that would separate us. The compound Fane wants. The one held by whoever the Directorate has to beg. That's the only thing that turns a decaying forgery into a permanent one." She let that sit. It was real, and it was frightening, and it pointed everyone's eyes at the precursor and the factions and away from the boxes on the forty-first floor. "So whoever this is will go for the same door we need. We'll meet them there."
Gideon held her gaze one beat past comfortable. "That's a reason to hurry the separation," he said. "Not a reason you'd want to."
"I want a great many things I'm not entitled to."
"Convenient," he said, without heat, and let it go. But he had marked it. She saw him mark it, the small internal filing of a thing that did not add up, and she knew he would return to it the way he'd returned to the lift panel, patient, certain the door would open if he stood in the right place.
Anika's reader chimed. She frowned at it, then frowned harder. "Huh."
"Don't do that," Mira said.
"The thirty-nine door." Anika turned the screen. The decaying lattice again, and beside it a timestamp, and beside the timestamp a second use of the same partial credential, minutes old, on a floor the display named without hesitation this time. "They used it again. Just now. And they didn't go down."
Gideon read it. Mira watched him read it, watched the stillness come, deeper this time.
"That's here," he said. "That's forty-one."
Somewhere below their feet, on the windowless floor that was supposed to be the one place the tower could not find them, a bad copy of their single name had asked a door to open.
And the door had said yes.