Terrence had sort of explained to Ella what had happened to him during the fight, but not really; she had her own issues to deal with, and the two of them had never been very good at talking. That was alright, though, because he and Ella were on the same page. He and Katie were so drastically not on the same page that when she asked, he actually answered.
"I got attacked," he said. He'd worked through a lot of his emotions regarding it, so there wasn't much in the way of negative emotion in his voice. "On Saturday. Well, they didn't attack me - they got Ella's little brother. And - did I ever tell you I would have had a sister, if she hadn't died when I was younger? Anyway, my head decided right in the middle of a fight was the perfect time to go crazy over that, and I had to leave before I knew either of them were safe to get myself to St. Mungo's."
Which probably sounded worse than it had been, to someone who didn't realize that he and Ella never protected each other, that Ella might never have forgiven him if he'd stayed and died, or ended up much worse off than he already was. Whether he'd stayed or gone, nothing would have changed, except for his own circumstances, since he'd been of absolutely no use to either her or Alek at the time. But that really wasn't the point of what he was trying to tell Katie now. "Apparently people are getting bolder, attacking Death Eaters in the middle of Diagon Alley."