The layers of confusion and surprise that are happening here are truly impressive. The question startled and confused Bruce. Bruce's answer left Zerxus in disbelief. Bruce is disbelieving that the answer isn't obvious.

Even abruptly understanding that it is being asked out of some sort of concern isn't less confusing. The whole thing does remind him of his childhood, though, and that isn't a time period he would like to revisit.

"I trust you alone in the Manor." Because he can give the man orders he must obey and also trust is not the right word, but whatever. It can serve as a deflection. "My father's the Lord of Hell."