On a deep brine extraction colony, crushing pressure and failing infrastructure have turned the lower galleries into flooding death traps. Staff Sergeant Thorne and a combat engineer squad enter to manually override Floodgate Manifold Theta-9 and prevent the lower shelf from being submerged. They deploy through pressure locks to cut through salt-crusted floodgates, but the corridors are already infested by the Hollows—an alien organism that converts human bodies and metal infrastructure into chitinous biomass on physical contact.

The extreme pressure and brine aerosols force the soldiers to rely entirely on their sealed Hardshell suits. But dormant biofilm has been surviving inside their suit filters, waiting for quorum-sensing triggers. As the squad burns through the fused remains of the previous unit to reach the manual override lever, th ...