But the primitive warning wouldn’t fade. She clenched clammy fingers around her phone and peered out of the storage room. She saw no one in the small beam of light. The corridor light switch was at the end of the hall, near the doors that led to the elevators and stairwell. All the doors on either side of the hall were dark and closed, just as they’d been when she went into the prop room. But none of them were locked. Anyone could be inside.

She moved faster, her imagination conjuring images of hands reaching out to grab her. By the time she reached the stairwell, she was nearly running. She paused at the door. Something whispered behind her, another soft brush of fabric on fabric. Louisa pushed through the door into the stairwell. She switched on the light and ran down two flights of stairs, bursting into the first-floor hallway sweaty and breathless. The hum of a machine drew her to the main corridor. A janitor pushed a floor cleaner slowly across the tiles, the path behind his machine clean and shiny with moisture. Glancing at the shoes in her hand, he raised a brow. She smiled and stopped to put on her heels.

Trekking down the main corridor, she spotted the security guard behind the reception desk near the front door.

The guard raised his gaze from his paperback. “Dr. Hancock.” He greeted her in his slight Slavic accent and a curt nod of his white-haired head. “Is everything all right?”

“Good evening, Serge.” Louisa took a deliberate breath to slow her racing pulse. “Are any of the other curators here tonight?”

He squinted. His head tilted as he studied her. “I haven’t seen anyone come in, but then, I didn’t know you were here. I was making my rounds until a few minutes ago.”

“You weren’t here when I came in,” she admitted. “I used the back door.”

“What is wrong?”

“I thought I heard someone on the third floor.”

“Probably the cleaners. Dr. Cusack is also here.” Standing with a wince, he came out from behind the desk, his posture painful and bent with arthritis.

Cusack didn’t frequent the storage rooms.

Serge cracked his neck. “Why don’t I go up and take a look?”

“I’d appreciate that.”

She followed him to the rear corridor. They passed the public restroom. A janitorial cart propped the door open. The sound of running water echoed on tile and steel. Serge’s jerky gait covered ground faster than Louisa expected, but he chose the elevators over the stairs.

On the third floor, he flipped on the hall lights. They moved from room to room in a cursory inspection. Thirty minutes later, after finding no one and nothing suspicious, Serge turned off the last light, and they returned to the elevator.

“Probably one of the cleaners,” he said. “Or a rat.”