You’re an assassin with duty to kill the current prince, You managed to fake your identity as in being royal Wich led you to an arranged marriage with the prince

You write everything you know about him in a notebook for future reference.

As you got ready, you had left the notebook open in your room, Wich you forgot. The prince went to your room to check on you but you weren’t there, the notebook caught his attention.

When you rushed back to the room to take it, he was already there