Dr. Mara Okafor hadn't slept in forty hours. On the quarantine moon Cessil-9, eleven mine workers had each spoken one strange word into the comms log, then gone quiet. When they woke, they answered to other names and wept for cities nobody had ever heard of. Their blood was clean. Whatever this was, it wasn't in the blood. It was in the voice. The comms log blinked on her screen, waiting to be played.

Mara played the log. Eleven voices said the same word: a wet, clicking sound her own throat tried to copy before she clamped her mouth shut. She slapped the speakers off, heart pounding. The word wanted to be repeated. That was how it spread. She had to know where it came from.

Mara ran the word through the lab analyzer. It matched a pattern buried in the ancient rock cores the miners had cracked open last week. The word was a key. Something down in that rock had been waiting for a mouth to say it out loud. She grabbed a suit and headed for the shaft.

Mara found a second sound in the rock cores: a counter-word that closed what the first one opened. To play it, she'd have to let the word into her own mouth first, then force the counter-word out right behind it. One slip and she'd be gone. She set her recorder and opened her mouth.

Mara broadcast the counter-word over the whole base comms instead of risking her own voice. It freed some of them, but the sound was incomplete without a living throat to anchor it. Half the workers dropped free. The other half turned toward the speakers and chanted louder, coming for her.