Plague of the Shattered — E.E. Holmes

Once every five years, the Northern Clans of the Durupinen gather at Fairhaven Hall. There at the ancient castle, surrounded by the very spirits they are bound to protect and serve, the clans settle disputes and shape the laws that govern the Gateways to the spirit world. For the first time, Jess and Hannah Ballard have to represent their clan. It is an awesome responsibility -- a great honor… and they are sure it's going to be the most boring week of their lives. Oh, how very wrong they are. For something dangerous is stalking the halls of Fairhaven. It lies in wait, striking down victim after victim, undetectable and inescapable. No one knows what it is, or what it wants, but one thing is clear: no one is safe until it is captured. As their fellow Durupinen fall victim one by one, it will be up to Jess and Hannah, the newest members of the Trackers, to solve the mystery before the entirety of the castle is possessed.