As she traversed the upper floor, April found herself distracted from the task at hand; she couldn't keep her mind from wandering and worrying. She took a deep breath and cleared her mind but moments later caught herself wondering how Mark was faring with the outer buildings. She huffed with frustration. She'd been trained better than this and she wasn't going to let the infuriating noise get to her.
Some unseen machine within the building was bombinating constantly in a pitch which rose and fell in different parts of the corridor with no clear pattern. It played havoc with her nerves and it wasn't hard to guess that that was its main purpose.
It put her on edge. It didn't help that she hadn't encountered a single soul throughout the entire building. To all intents and purposes, it seemed to be deserted. But it shouldn't have been. Any moment she expected to see a THRUSHee turn the corner and catch her in the act of investigating the satrap, but nobody ever did.
She approached another door to a thrumming crescendo and could feel her muscles tense up in anticipation. Forcing herself to relax, she slipped through the door and into a room of pure darkness.