Barty jumped and instantly felt ashamed. He had thought he had been trained well enough not to show that he was surprised, but then maybe Azkaban had leeched that power out of him as well. You could take the boy out of the prison....
"Yes sir," he said, standing up straight and to attention. He did not offer a hand, as that would be presumptuous, instead he waited for the other man to do so. He couldn't help but look curiously up into the Grindelwald's face. Almost normal-looking, he thought, certainly much more... human than Voldemort had looked during those last few months. "At your service," he added, with a respectful bow.