Stronghold – “Good, bad, and bloody” [6th campaign – 2nd mission]

Hello, I have a problem in the first mission. I chose the Path of Blood, and in the second mission, I wanted to change it, but to do that, I needed to free 3 rebel slaves. I freed them, but the gate to Airu didn't open, and nothing happens. Is this a bug, or am I doing something wrong?