After the fall of the kingdom, everyone in England has divided themselves into thirty-nine communities, each based within a castle. This is the way that people live now - in a future that seems like the past.

Eleanor Conway is part of the secret organisation Castle Seven, charged with taking part in missions on behalf of the Clearheart Community. But Castle Seven is now Castle Six, following Anderson's dramatic departure.

Anderson has kidnapped Eleanor's friend Mary. He tells her she is destined to be Queen of all England one day - but can she trust him?

Eleanor and the Castle Six make preparations for a rescue. But by the time they end their adventure, they're destined to be one less in number.