Antonin somehow managed to discover they had given her a place to hide, a place to relax and almost feel normal again. Even though it was clearly a violation of the treaty the Dark Lord made with the witches and wizards of Wales, he'd gone straight to their home. She didn't need to read the accompanying articles to know what happened. Likely, they were all full of propaganda and lies anyway. Antonin probably demanded to know where she had gone and when they didn't answer, he became angry.