Callista stumbled, her breath ragged, as the stone corridor stretched endlessly before her. The narrow passage was cool and damp, the air thick with the scent of earth and something faintly metallic. The light from the ceiling—soft, artificial, and sparse—offered just enough visibility to keep from walking straight into the wall.

She barely had time to adjust to her surroundings.

“Sam—” she gasped, yanking at her arm. “Sam, stop. Where the hell are we going?”

But he didn’t stop. ...