The Barracks can be found in Mythrad. The current head of the guard is Rheshus Haggor.

The Barracks is surrounded by a solid stone wall, with an entrance to the South, guarded by a watchtower. There is a small arena in front of the main building stocked with various weapons. At the opening stand two young men, who are guarding the place.

‘What business have you here?’ One inquires. If the party has no suitable answer they are turned away.

If the party gain entrance to the Barracks:
As you walk past the arena you notice two men sparring with wooden practice swords in the corner, they appear well versed in the art of combat, and each blow cracks across the courtyard. Inside the barracks is a large mess hall, which is clean and ordered, with Mythrad’s banners hanging off the walls, and a small kitchen in the read. Upstairs are the men’s chambers, which can house the city guard of 16. There are a few men relaxing in there, others are cleaning their weapons and fixing armour.
The watchtower is a sturdy structure of wood and stone. On the first floor is the office of Rheshus Haggor, who is the head of the guard (25% chance to find him there). The next level is open, and stocked with archer’s equipment.

If you already know Rheshus is a traitor, you can go in and question him, and then try to reprimand him. You can fight him and when he ‘dies’, you can pick to execute him there and then or take him to the prison.