Very good so far. I liked the taste you've given us.
A few things, though. The dialogue seemed a bit strained, as in, it doesn't seem like a seventeen-year-old would speak like that.
I don't think there were any mistakes: none that I could find, anyway.
One suggestion, and this has nothing to do with writing rules or anything like that; when you begin a new paragraph, skip a line.
For example:
" BANG! BANG! BANG! A loud rap on the door interrupted the silence in the room. A girl of about seventeen stormed in. It was Charles’ two years older sister, Erin. She had her raven black hair tucked into a sleek ponytail and her honey-golden eyes that matched his, glared around the room. Her porcelain skin was flushed with excitement.
“I found the right information! We just need you to analyze it,” Erin exclaimed, clutching a sheet of paper and waving it in his face."
Since people are reading it from a computer screen and not a book, it helps it A) Look neater and more tempting to read and B) Helps the reader understand when one paragraph ends and one begins.
Besides that, excellent beginning!
