For what I understood, the knight was pissed with the family because shuli was going before the wedding happen, so he leaked the info to his "friend"... His friend, brainwashed by the cardinal (and the church) told him this and then he used it to kill shuli to his personal desire and to "reinforce" their influence to the empire to make the empire began a war against another country... I don't know, but I think this friend, seeing how the knight was abandoned will spill the beans and will be from him that nora will get the info he needs