"Thud!"
A dull sound, like something heavy lightly striking thick metal, rang out abruptly through the tangled ventilation network beneath the lower decks of the Opal Dragon-class battleship Scharnhorst. The ducts amplified it into a hollow, distant echo that spread in every direction through the cold, winding metal passages.
The warship was in its artificial night cycle. Lighting in most areas had dimmed to its lowest setting, leaving only emergency indicators casting ghostly green or dark red halos. The air carried the faint chill of recycled, filtered air, along with the ever-present low hum of the engines and Life-Support System.
That thud was like a stone dropped into a silent, deep pool, jarringly loud.
"There it goes again!" In a narrow maintenance passage beneath a nearby duct junction, the crewman Rann leaned beside an open inspection panel, wiping a wrench with a filthy grease rag.
He paused, tilted his head to listen for a moment, then rolled his eyes at his companion, who was replacing the power pack in a portable promethium lamp. His voice was full of weary irritation.
"Hear that? That bloody noise again! Lately, every time 'night' comes around, this damn stretch of duct acts like it's haunted. Every so often, it goes 'thud, thud, thud,' and never gives us any peace! I've checked the maintenance logs eight hundred times. Not a damn thing wrong with it! Bloody unnatural!"
His companion, a young technician with a fresh welding scar on his face, shrugged and was about to reply when Carl, the old crew member known as "Old Pipe," let out a low chuckle nearby. She was squatting on a toolbox, her hair graying and her face marked by engine oil and age, and her grin revealed several missing teeth.
She deliberately lowered her voice, hoarse from cheap