After receiving a mysterious coded message, Zen Starling abandons his life of luxury and, with the help of sentient trains, goes in search of android Nova, who plans to reawaken the Railmaker. The Great Network is changing. New worlds, new alliances, new enmities. For Threnody the changes have brought great power. For Zen and Nova they have brought separation. For the trains that run from world to world, they have brought questions. Now all of them must find out what really matters to them and who they really are