The abandoned Observatory annex provided Elara with the one thing she desperately needed: time and quiet. Huddled over an oak table littered with star charts and discarded astronomical instruments, she pinned Laurent's cryptic note alongside an immense, detailed 1:500 scale map of Paris.
The address, 14 Rue de Valois, 17th Arrondissement, placed the holding cell far from the historical core—a deliberate choice by the Argentum Society to ensure anonymity. The building was identified on the old maps as a discrete former coach house, once an annex to the estate of a minor noble family.
Elara focused on the four geometric points Laurent had sketched: three forming an uneven triangle, and the fourth centered precisely within it.
"He wouldn't use simple coordinates," Elara murmured, tapping the pencil against her chin. Laurent, an archivist, thought in layers and references. She realized the geometric points weren't physical locations; they were anchors for a historical triangulation.
She pulled down a heavy ledger from the annex's shelves—a detailed municipal report from the late 18th century detailing property divisions in the 17th. Cross-referencing the Rue de Valois address with the surrounding estates, she found the connection: the property had been briefly owned by the descendants of Elias Argent, the Society's philosophical founder. The coach house was known to have been used by Argent's family during the tumultuous revolutionary period to secure priceless, often questionable, assets.
"A place designed to hide treason, not just people," Elara deduced. "It's a vault."
The three outer points of Laurent's sketch matched three specific, small, and rarely visible architectural features of the coach house: a drainage pipe, a bricked-up window, and a ventilation grate. The centered fourth point, however, did not correspond to any known feature.
The centered point had to be the weak link—the secret entrance. But without a physical marker, how was it hidden?
Elara remembered Jules's haphazard filing system, particularly his notes on 18th-century municipal code and construction disputes. She spent an anxious hour searching the empty annex, finding a dusty box Laurent must have retrieved for Jules, containing copies of old Parisian planning applications.
Finally, she found a handwritten note by Jules on a construction dispute concerning the Rue de Valois property in 1789. The builder had complained that the owner (Argent's heir) had insisted on an illegal, subterranean delivery shaft be built into the foundation to move goods discreetly. This shaft, located exactly beneath Laurent's central geometric point, was subsequently sealed from the inside.
The delivery shaft. A narrow, forgotten entry point, built for secrecy, not security.
"They brought Jules in through a servant's entrance," Elara concluded, a plan forming in her mind.
The shaft was too small for Dubois's large agents like Henri to comfortably use, but perfect for her small frame. It was her entry point, but she needed to locate the precise access panel on the outside, likely through the ancient municipal sewer system.
Elara could not risk exposure by purchasing equipment, so she gathered what she could from the annex's forgotten stores—the tools of a desperate scholar.
The Sedative: The annex had an old, unused chemistry station for astronomical photography. Elara mixed a concentrated, fast-evaporating compound based on an antique conservation formula—a harmless but highly potent sedative gas, designed to safely render fragile artifacts inert for transport. Contained in a small glass flask, it was her only weapon.
The Acid: She found an extremely high-concentration, industrial-strength acid used for etching glass lenses. She diluted a small amount for the purpose of silently dissolving a specific mortar joint or a small lock mechanism, avoiding noisy crowbars.
The Map: Most crucially, she retrieved an immense, hand-drawn map of the 19th-century sewer and service tunnels beneath the city, a map Laurent had kept for decades, originally intended for academic study of the city's water flow. It showed a direct path from a known, public manhole to the basement level of the Rue de Valois coach house.
She equipped herself: the two keys secured in a hidden inner lining of her dress, the acid and sedative flask in a protective leather pouch, and the sewer map clutched in her hand. She was ready to return to the darkest veins of the city.
Before leaving the sanctuary of the annex, Elara paused. She picked up one of Jules's typewritten, unpublished rants about Parisian corruption, signed simply: J.R.
She quickly typed a small note, folding it into the document:
If this document is discovered before sunrise, and I am not present, publish it. Use the name Argentum. The truth is buried beneath the Panthéon. —E.
It was a contingency—a final insurance policy. If she failed, the exposure would still cripple the Society.
She placed the note inside a heavy, bound copy of De Arte Chymica, left conspicuously on the table.
She stood ready to descend into the cold, chemical-laden world of the sewers. She was leaving the light of academia for the shadows of action. She was no longer just saving an artifact; she was saving the life of the man who risked everything for her. The burden of Loss had turned into the power of Resolve.
The time for planning was over.