Cadence was proud of herself. Even though the hunt the night before had completely exhausted her, she still managed to make it into the gym by 10:00, only an hour later than usual. She was surprised how deserted it looked, however, but when she walked into the room that housed her favorite treadmill, she had to do a double take. “Christian? What are you doing here?” she asked, clipping her water bottle into the holder and tossing her towel across the frame as she fastened herself to the dead man and started up.

“Well, I usually run in the middle of the night, while you’re fast asleep, but since we...