The Moon rang like a bell.

Not natural. Not human.

Six months later, an international mission drilled into the Oceanus Procellarum region, where gravitational anomalies were strongest. The drill bit chewed through three meters of regolith, then punched into empty space. Cameras lowered into the borehole revealed a cavern so large its far walls faded into darkness. And on those walls—faint, phosphorescent glyphs.

“That’s not possible,” whispered her colleague, Dr. James Okonkwo, peering over her shoulder. “The Moon’s supposed to have a small iron core, maybe some partial melt. This… this is structured.”