How your past can come back to haunt you. Ash would have never gotten caught up in this mess if his own past was not used as leverage against him. Its also about how bad people with power can influence people to do things they never thought that they were capable of. It is also about how two people who can have almost nothing in common can work together and accomplish tasks they set out on. Overall it seems like the author is trying to show us that no matter what action you take it always has a consequence.
Read more: THE WOMAN FROM PRAGUE