No one has ventured into the sixth layer of the Abyss and remain 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 most unsettling thing of all is the ruins of the Golden City. Here each of the delvers will be forced to forge their own destinies and paths as they investigate the city's mysterious origins and the strange beings who still dwell there. The answer to their questions, as always, lies somewhere ahead, down and forward…