Filed Late Throat

The chamber throat did not narrow. It withheld—stone keeping the width of a published corridor while the air insisted the room beyond had been measured on a different day.

Eris held the lantern low. Condensation on the walls ran in ruled lines parallel to her margin scratch, as if the flats were still arguing with themselves about which draft of the map was law. The Violet Compass needle hovered at through, not north, violet honesty trembling on a bearing she had paid for in stolen chord and symposium ink she did not trust.

The door was not hidden. It was filed late—a slab set flush where the inward fork's charts showed only bearing pool and dead end. Someone had chiseled a catalog mark beside the seam after the expedition's charter was stamped: MS-11 / THROAT / REV B. Revision B meant the first survey had lied politely.

Eris pressed her gauge-card to the seam. Lichen resonance guttered; unlicensed filament memory in the card's gutter brightened once, the way a witness line remembers stress without replaying speech.

"You filed after we walked," she said to the stone. "That is either incompetence or invitation."

The salt-signal tugged—not hunger, not thief. Through.

She worked the seam with her thumbnail where wax from the symposium capsule still clung. The slab gave on a bearing click too small for harbor tiers, too precise for cavern guesswork. Mirror Spring engineering: a door that opened only when the flats agreed you had spent enough margin to deserve the correction.

Beyond, the air changed temperature the way sealed laboratories changed permission—colder, drier, glass-throat honest. A short vestibule of mirrored salt faced her, ceiling low enough to force cartographers to bow or lie about their height. Starlight pooled on the floor in shapes that were not constellations any triad had ratified. They were offsets—the same sky, filed on a parallel index.

The compass needle jerked toward the nearest pool and then away, as if ashamed of appetite. Eris knelt. The pool's surface held no reflection of her face. It held bearing debt rendered as ripples: concentric rings counting steps she had not taken yet.

Footsteps resumed behind her—still out of phase, still Syndicate rhythm on stone that had never known harbor—but the margin line beside the shelf was gone. Whoever had stolen bearing had either paid or fled into revision B.

Eris stood. "I am not your receipt," she told the empty vestibule, and meant the symposium as much as the thief.

She scratched the mirrored floor parallel to the offset constellations. The scratch rang. The ripples stilled. The Violet Compass named the next bearing in violet ink that did not flicker:

THROUGH / REV B / WITNESS THE INDEX

Above the salt, somewhere past glass and charter, the symposium stumble she had delayed found a new footing—not forgiveness, attention. Eris felt it as pressure against her sternum, the way a sealed lab exhales when an instrument fails triad and must show its work to someone who kept walking margin anyway.

She capped the lantern to a thin blade of light and stepped into the mirrored vestibule. The door filed late sighed shut behind her—not trap, archive. The flats did not forget revision B once a cartographer paid the bearing to read it.

Ahead, the throat opened into a geometry the published charts called impossible: a fork where both paths had been walked on the same day, filed on different pages. Eris lifted the compass. The needle did not hesitate.

She intended to publish the offset if she survived it.