See Imperial Order for the original version that didn't appear in the game. The text after "Tullius" may be cut off and not appear in-game.
To commander Northwatch Keep:
The agent bearing this letter is to be escorted to Thorald Grey-Mane, a prisoner at Northwatch Keep. The prisoner is to be transferred into the custody of the agent and granted safe passage from the keep.
By authority of General Tullius, Imperial Legion, Solitude.