In a large kingdom, there is a ruling family that has over one hundred members. Every ten years or so, they gather together in a reunion. Each member wears a pendant showing the number that they are in line to the throne, which are switched around at the reunion. Which region they rule over is determined by this line, with those highest in the order of succession closer to the seat of power at the center of the kingdom.
At the reunion, five years prior to the main events of the book, there is an uprising and thirty or so of the royals are killed on the spot. The rest manage to escape, going on the run as the uprising has a huge following and the kingdom is no longer safe for them. People are hunting down the royals for honor and glory and the like, with people collecting the pendants to show how many they had killed. Some just buy the pendants, or kill the killers for them. About thirty or so of the royals sold the pendants themselves, and are hiding out among the people, pretending not to be royals.
The main character of the book is hunting down the last of the royals. They meet one of the royals without knowing who they are, and the two head out together for some reason. The royal is trying to work against the main. Plot happens.