To a noble family twins are born: Mathilde and Giselle, the Sisters Grey. For generations the Sisters have protected and counseled the Kaiser, ruler of Mitteleuropa. But this is a different time. At the birth of the industrial age a great war is raging. When the Kaiser is assassinated, Giselle is accused. Pursued by her sisters and hunted by the enemy, Giselle must unravel the prophecy of the Carbon Grey before history itself is rewritten.