Sofia's POV
"Keep breathing slowly, Sofia," Jack’s voice drifted through the pitch-black void. "Deep, measured breaths. Panicking only burns through the oxygen faster."
I sat with my back pressed against the cold steel of the vault wall, pulling my knees tight against my chest. "How long do we have?"
"A few hours, maybe," he replied softly. The sound of his footsteps echoed as he moved around in the dark, feeling along the seams of the massive vault door. "Aria was lying about three hours. A vault this size has enough sealed air for at least six or seven. But we can't afford to just sit here."
"She had a birthmark, Jack," I murmured, my voice trembling as the reality of it settled into my bones. "A birthmark just like mine. Aria... she's my sister. My actual twin."
A heavy silen
