Six thousand meters down on the ocean floor, the corroded fuel security facility of Blackwater Lock Twelve is failing under the weight of the water. A massive infestation of Gravemaw beasts and their corrosive bacteria is expanding through the flooded lower levels, cracking the pressure hull and threatening to trigger a catastrophic implosion of the entire continental shelf lock system. A small pathfinder unit of the 21st Drowners is deployed into the freezing dark to secure the ballast plant and hold it for a heavy repair submersible.

The Gravemaws claim territory through sheer crushing mass, but their juveniles exhibit a far more disturbing behavior. They excavate human corpses, burrowing into the dead tissue to create moist, protected nests, treating the fallen crew as nothing more than terrain. As the pathfinders navigate the ruined pum ...