The smile remains, although he wants to recoil from the predator of equal strength. Part of him says that the man is challenging him, directly, publicly, homing in on the weakest in the room like a shark. The more rational part recognizes a fellow Carthian being sociable, greeting him after his long absence from public view.
The smile remains, light and welcoming. Maybe this is an opportunity.
"Mr. Hall, it's good to see you again, I trust you've been well?"
Not that he trusted anything, but using key words like that often put others at ease.