Marcello’s voice, thick with triumph, echoed in the sudden, absolute dark. Cosima, still clutching the precious vial, felt the air shift around them, not just with the absence of light, but with an unsettling, profound change in pressure. The arcane symbols on the vault’s inner door, which had pulsed with a faint, sterile blue during their earlier access, now flared a virulent, sickly green, then died. A low, grinding hum, utterly unlike the steady thrum of the Conservatory’s usual ventilation, vibrated through the steel floor. “No,” Cosima whispered, her voice a thin ribbon against the growing pressure in her ears. She knew this sound. It was the reversal cycle, a failsafe on the deeper, more secure vaults, meant to sterilize the contents by creating a vacuum. Or, in their case, to suffocate anything trapped inside. Bastian, who had been cursing Marcello under his own reduced intake of truth-gas, pushed off the vault door. He stumbled, his hand flying to his throat. “What in the blazes… the air, it’s… thin.” His words were already slurring, the residual gas and the rapidly depleting oxygen compounding. He swayed, his broad frame suddenly unsteady. Cosima scrabbled in the dark, her free hand sweeping across the polished steel shelves she’d just emptied. Her fingers brushed against something cold, hard, and cylindrical: a small, self-contained emergency respirator, one of Marcello’s paranoid luxuries. She snatched it. A single, sleek silver canister, no bigger than her forearm, with a collapsible mouthpiece. Enough for one. “It’s a vacuum seal,” she gasped, forcing the words out. “He’s sucking the air out. There’s… there’s only one.” She held up the canister, its metallic gleam catching the dying green phosphor. Panic tore through her. Bastian’s head snapped up, his eyes, even in the near-dark, burning with a fierce, possessive fury. “One? Then you take it, Vettori. We need that antidote.” He took another gasping inhale that produced little but a rasp. Cosima shook her head in a frenzied refusal. The air grew thinner, each attempted draw burning in her lungs. The truth-gas stripped away her defenses, tearing down the protective walls of cynicism and sharp wit. All that remained was raw terror for Nico, and the hollow ache that would follow if she failed. “I can’t,” she choked out, her voice cracking, shorn of all its usual bite. Tears, hot and shameful, streamed down her face, the first she’d shed in years. “Gods, Bastian, I can’t. If Nico… if he dies because I couldn’t get this to him, because I wasted too much time playing Marcello’s games… I can’t. He’s all I have. He’s my purpose. I… I can’t breathe, Bastian. I can’t.” The vacuum pressed down on her, stealing her senses. The horror of failing Nico, of leaving him to perish alone and choking in the smog, dragged her to her knees. Another confession spilled from her lips, torn out by the vapor: “I shouldn’t have left you. That night. I shouldn’t have walked away.” The words were barely a whisper, an unbidden plea. Bastian moved. He was slower, his limbs heavy, but his movements were deliberate. He took the canister from her trembling grasp, his thumb brushing her wet cheek. His gaze, though clouded with hypoxia, held hers with an intensity that pierced through the haze. “You didn’t have a choice, Cosima. You just hate how it ended. There’s a difference.” He coughed, a dry, rattling sound. “And I’m not letting you die in here. Not like this.” He brought the mask to his lips, but instead of inhaling, he shook his head, pushing it away. “Not just for me,” he rasped, his eyes fixed on hers. “There’s no point in saving one lung if the other collapses.” He lifted the mouthpiece to *her* mouth, pressing the smooth rim against her dry lips. “Breathe, Cosima. Take it.” “No!” she protested, weakly pushing his hand away. “You’ll die, Bastian! The antitoxin… Nico needs it, but you… you’re still dosed with the truth-gas, you need air, too.” He laughed, a short, humorless sound that ended in a wheeze. “Small mercies, then. My secrets are already out. Yours, though… you still need to scream them from the highest spire in Canto. Not here. Not now.” He leaned in, his face inches from hers, his eyes dark pools. “We share, Vettori. Or we both go down. Your choice.” She hesitated for only a fraction of a second, brutal logic cutting through her panic. With a shaky hand, she took the canister. Her paranoia shattered. She couldn't do this alone, and she refused to watch him die while he offered her life. Cosima took a deep, shuddering gulp of the recycled air, feeling the sweet, life-giving oxygen flood her starved lungs. Then, without a moment’s further thought, she pressed her mouth to his, forcing the mouthpiece between their lips. Her hand seized the nape of his neck, pulling him closer to force every scrap of oxygen between them. It was survival stripped bare, yet as their lips met around the valve, heat flared between them. His arm locked around her waist, hauling her flush against his chest in a fierce, crushing hold. Recycled oxygen, the bitter residue of truth-gas, and the salt on her skin mingled into something sharp and intoxicating, turning the struggle for breath into a ferocious collision. They broke apart, gasping, their chests heaving, eyes locked in the near-dark. His pupils were dilated, his breath coming in ragged, shallow pulls. He swayed again, his grip on her slackening. “Bastian!” she cried, feeling his weight shift, his body going limp. He was losing consciousness, his system starved of oxygen. His head lolled to the side, his eyes fluttering shut. Just as his massive frame began to slide down the cold steel of the vault wall, a deafening *CRUMP* ripped through the antechamber. The entire vault shuddered violently. Then, with a scream of tortured metal, the heavy brass and steel door imploded inward, tearing from its hinges with explosive force. A surge of rancid Canto smog, mixed with the acrid tang of burnt alchemical charges, rushed into the vacuum. Through the swirling, toxic haze, a figure stumbled into the breach, coughing violently. It was Nico. His face was streaked with soot and sweat, his clothes singed, and in his hand, a heavy, jury-rigged detonator box, its wires sparking. He collapsed onto the debris-strewn floor, the vial of antitoxin clutched tight in Cosima's hand suddenly feeling heavy with promise.

Breathless