The Never-Stopping Doomsday Train

When the 'Grey Tide' descends, nanomachines devour everything. Humanity's last civilization huddles on a never-stopping maglev train—the Loop Federation. Shen Fu, a train engineer, dies in the Grey Tide during a supply mission. He opens his eyes again, 48 hours before the disaster. Only two days. He must convince the Federation's high command of the impending apocalypse, find a way to stop the Grey Tide, and survive the assassins of the 'Revisionist Faction'. But every change tears the timeline. As he nears the truth, a more terrifying question emerges: Was the Grey Tide really an accident? Or is someone deliberately restarting humanity? One-line hook: An engineer travels back to 48 hours before the apocalypse, racing against time on a never-stopping train to uncover the shocking truth behind the nano-apocalypse.