Plotting?

[Giulia]

Hellooooo everyone!
I'm writing a political fantasy story and I'm rather stuck on, well, the politics of it! Basically, here is my dilemma:
My story is centered around royalists trying to protect the kingdom from rebellious groups - three of them, to be precise. I want to have a character who advises the king and appears to be working for the other side but actually is working for the royalists - he's a double agent. I need some instances where she would catch him 'double-crossing' but he's actually helping the royalists?
I know this is pretty vague but if anyone has any tips or incidents that you could help me out with, I'd appreciate it! :)

[Giulia]

I like the speech slip ups, that's good...my original plan involved fake messages passing to the actual spies and real messages passing to the advisor but our main character doesn't know that so she assumes he's the with the rebels...