Chapter One

The lights had been on emergency for six hours when the intercom clicked.

“Protocol is live,” the voice said. It was the bunker’s automated system, calm and flat. “Fertility window opens in ninety minutes. Designated pairings will report to Chamber Three. Compliance is required.”

Marcus sat on the edge of the cot and stared at the floor. The air recyclers hummed. Somewhere deeper in the bunker, water dripped into a catch tank. Outside, the upper levels were gone—collapsed, sealed by the blast doors that had dropped the moment the sensors registered the pressure wave. No one was coming. Not tonight. Maybe not for weeks.

Across from him, his daughter Elena pulled her hair into a tight knot. She was twenty-four, still in the clothes she’d been wearing when they ran for the elevator: jeans and a thin tank top. Sweat had darkened the fabric between her shoulder blades. She didn’t look at him when she spoke.

“They said the serum was already in the water filters,” she said. “We drank it with lunch. My skin’s hot.”

“I know.” Marcus’s voice came out rough. He cleared his throat. “Mine too.”

The protocol had been written years ago, when the bunker was still a joke the family told at holidays. If the surface went bad, the sealed lower level would keep a small group alive. The fertility clause had been added later, after one of the engineers pointed out that a multi-month isolation with only a handful of adults would eventually require replacements. No one had expected to use it. The pairings were listed on the laminated card bolted beside the door of Chamber Three: Marcus and Elena first. Then the others. Rotation every twelve hours until the window closed.

Elena stood. She wiped her palms on her jeans. “Chamber Three’s the one with the exam table.”

“Yeah.”

They walked the short corridor without speaking. The door opened on a bright room that smelled like antiseptic and the sharp, chemical edge of the serum. The table was padded, stirrups folded back. A cabinet stood open, supplies already laid out. Elena stopped just inside the threshold.

“Dad,” she said.

Marcus shut the door. The lock engaged with a soft click. “We don’t have to talk about it. Just… do what it says.”

She nodded once. Her fingers found the hem of her tank top. She pulled it over her head and dropped it on the floor. The bra followed. Her breasts were flushed, nipples tight. The serum had already started its work; he could see the faint sheen on her skin, the way her breathing had gone shallow.