On the decommissioned Charybdis Anchor deep-sea platform, a flooded and spore-infested interior has become a breeding ground for a parasitic organism that hijacks human neural tissue and suit systems. The surviving members of the 7th Recon descend the vertical shaft known as the Spine to leave their fallen sergeant's tags at the bottom moon pool. But the organism has already infiltrated their ranks, puppeting compromised crew to deploy armored ambush forms directly into the squad's formation.

The team attempts to push deeper by initiating a saturation fire protocol, burning shotgun slugs into the ceiling voids of every new compartment to keep the mature forms at bay. The organism answers by corrupting their bio-monitors, flatlining the readouts of subverted hosts to hide the attack. As the squad burns through their limited ammunition, the o ...