"In search of the mysterious element known as aether, Claire Dulac flew her hot air balloon toward the edge of our stratosphere--and never returned. Her husband, genius engineer Archibald Dulac, is certain that she is forever lost. Her son, Seraphin, still holds out hope. One year after her disappearance, Seraphin and his father are delivered a tantalizing clue: a letter from an unknown sender who claims to have Claire's lost logbook. The letter summons...