Mara found the first route mark where no route had any reason to be: in the lower margin of a brittle accession sheet, tucked beneath a stamp that had outlived three directors. It was not a symbol from the archive guide, not a shelf instruction, not the private shorthand of any cataloger whose notebooks she had studied. It looked like a small river drawn by someone who had only heard water described from another room.
By noon she had found four more. Each one sat beside a record that had been corrected, renamed, or quietly moved out of public view. The ledger on her desk gave no explanations. It only offered dates, initials, and a sequence of colors that matched the tabs on boxes no current employee admitted to owning.
The transit room was supposed to be empty. Its brass plate had been removed, its key retired, its existence reduced to a line item in a building audit. But when Mara held the page against the window, the marks aligned with the old floor plan in the exact shape of a door. Behind that door, someone had been preserving a second archive, one made from the records the first archive had chosen to forget.
She photographed nothing. The ledger had already taught her that proof could become bait. Instead, she copied the marks by hand, sealed the page back into its sleeve, and wrote a note to the only person who would understand why a map could be more dangerous than the place it led.
Revision note: Mara returns after midnight with a conservator's lamp and discovers that the route marks fluoresce in the generated palette's green-blue range, revealing a fifth coordinate hidden under the accession stamp.