Emma had always laughed at travel tips that sounded too simple to matter. On a solo business trip, she checked into a historic mountain hotel where every hallway seemed to echo with strange creaks. Before climbing into bed, she remembered reading that leaving the bathroom light on, or cracking the door so a soft glow escaped, could help the brain stay oriented in an unfamiliar place. Smiling at the thought, she left the bathroom door slightly open. A warm ribbon of light stretched across the carpet, making the room feel a little less foreign and a little more welcoming.

Hours later, Emma awoke to complete silence except for the faint hum of the air conditioner. The glowing strip of light still pointed toward the bathroom, but another shadow slowly crossed it. Someone—or something—was standing between the bathroom and her bed, perfectly still, as her heart pounded in the darkness.