Fourteen kilometers beneath an ice crust, the Trench Ghost enters a supercooled brine ocean to survey Pump Gallery Seven-Brine, a flooded deep-crust sector corporate marked as sealed after a blowout. Chief Engineer Valya Kessel, Lieutenant Renn, Dr. Aris, and Captain Lin follow a manufactured sonar return toward an object frozen in the ice, while Stilt-Drakes move through the submerged station tunnels below.

The crew sends a drone into the gallery. But the cold, pressure, microbial growth, and false schematics turn every reading unreliable, and the three-tone chime begins sounding from a floodgate that should be dead.

This is "The Three Tone Chime" by Sascha Schmidt