This book is an alternative history of World War I. It retells the story in a way that could have happened if there was much more advanced technology at the time, technology that we don't even have yet today. The book it told from the point of view of the two main characters, Alek and Deryn. Both are keeping secrets about their identity, and if those secrets are revealed to the wrong people, the results could be disasterous. Alek's and Deryn's stories come together at the very end of the book, and their meeting could either help or ruin the other's secret. Even though they are on opposite sides of the war, they can each use the technology of their respective sides to create something even better. Will it all turn out for the better?