Hermione's first impression of Professor Reilly wasn't exactly favorable.
When she'd first seen him, it was the first day of classes. The Gryffindors had walked into the DADA classroom, not knowing what to expect, and they had been presented with him.
Professor Reilly looked almost as young as her, and he had an American accent, which was an oddity. The man was sitting behind his desk, worn boots propped up on the wooden surface, playing with a wickedly honed dagger like it was a toy. On first sight, Hermione doubted his ability to teach them anything.
And then, he shocked the class by saying his 'things that go 'bump' in the night' line, and dismissing them. Hermione looked it up in Hogwarts: A History, later, and discovered that Professor Reilly's first class was one of the shortest in the entire time Hogwarts had operated as a school. Further discussion with other years and Houses made it clear that he'd given them all the same 'speech'.
No, Hermione's first impression of Professor Reilly was not good at all.
His second class was a bit different, however.
"As I stated last class, my name is Professor Reilly, I was born in Los Angeles, California, and I have spent most of my life killing things that were ripped straight from your darkest nightmares. In this class, I will teach you how to defend yourself against these monsters, because, again, as I stated last class, if given the chance, they will kill you. If I manage to teach even one of you how to protect yourself, and the people you love, against these things, I'll consider it a job well done."
The look in the professor's eyes said that he had much too much experience in losing people he loved.
"Okay." He said into the awkward quiet that had fallen over the classroom. "We'll start simple. Who can tell me what a Hellmouth is?"
No one was all that surprised when Hermione's hand shot up into the air.