"That's how," said Hermione. She carefully traced what looked like a healing scratch. "It can't happen again - he's gone completely. Zach's certain of it, and yes, I *know* he's a prat, but he's one of the best Healers they have."
She wasn't going to tell Ron that the Squad's medical consultant had confirmed Zach's findings as a personal favor to Hermione. Not until they knew exactly what had triggered Grindelwald's appearance.
"You're safe, Ron. Safe. He won't - he can't do this again."