Living in Sunnydale, California was Hell on Earth, literally. The town was located directly on top of a Hellmouth.
Of course, most of the population was unaware of this fact.
First and foremost, the was Buffy Summers, the slayer. Buffy knew pretty much everything there was to know about offing those curious little beasties that crawled out of whatever hole hell creatures could find to crawl out of.
Then, there was Rupert Giles, your typical British, know it all librarian. He was also Buffy's Watcher. Whatever information you needed, it was an near guarantee that Giles could figure it out for you.
Accompanying The Slayer and The Watcher were Willow Rosenburg (the resident witch) and Xander Harris (the resident comic fan).
As far as most people were concerned Buffy and her group of scoobies, were the only thing standing between Sunnydale and Hellmouth USA.
This, as is often times the case, was not entirely true.
No, there was one other person in Sunnydale who was aware of the situation. One of the few people crazy enough actually STAY in Sunnydale after she found out.
Her name was Kathrine Moretti, and she was anything but scared.