No one has ventured into the sixth layer of the Abyss and remained unchanged. No one returns from their Last Dive, and no one knows what happened to those who delved further. Even with the possession of a White Whistle, an ominous specter hovers above Riko, Reg, and Nanachi as they advance down to the sixth layer, the Capital of the Unreturned. The pathways are more treacherous, the environment harsher, and the creatures even more dangerous, but the...

Colonel Samantha Carter takes charge as the city's new leader, facing new and daunting challenges, including joining forces with the dangerous Wraith in order to fight a common enemy-- the seemingly unstoppable Replicators.