So the final thing is... uh. Watch the ways that someone could be communicating with the enemy and try to get to those messages! At the same time, try to start peace talks with the enemy and find out more about the traitor from them too, so there's nothing for him to use against them and he's exposed! And the king should try to learn more about the people who could be traitors, while being protected so the traitor can't kill him if he realizes what's going on! Coming at it from a bunch of different directions and trying to stop a war at the same time—!