Antonin's sigh and initial refusal to answer the question proved that he was holding back. Even before she was an official interrogator for the regime, Hermione had already figured out his tells. Not that he was a terribly expressive man. No, she just knew how to read him. Once she discovered there was more behind the man than just the terrifying fury she'd seen in battle for her life, it was easy to tell when he was reluctant to speak.