Since Fighting Instinct, the survivors have settled into their new homes back on land. While half of the group has chosen to remain living underground in the Black Box, growing crops on the land above, the other half has made the decision to settle in the container yard down river, gathering much of their supplies through scavenging. By trading equally between themselves, the two colonies have managed to create a sustainable, and even comfortable, existence. When a team of scavengers goes missing, however, and a platoon of hostiles arrives on the Black Box's doorstep, the camps are prepared to show their fangs, to hold onto what's theirs by any means necessary. But something even more deadly than raiders is on the horizon, and it has far more teeth.