Synopsis from Goodreads:Kate Lowry didn't think dead best friends could send e-mails. But when she gets an e-mail from Grace, she’s not so sure.
Sent: Sun 9/14 11:59 PM
Subject: (no subject)
I shouldn't be writing.
They'll hurt you.
Now Kate has no choice but to prove once and for all that Grace’s death was more than just a tragic accident. But secrets haunt the halls of her elite private school. Secrets people will do anything to protect. Even if it means getting rid of the girl trying to solve a murder...
Happily Ever Ending:
Kate uncovered the Sisterhood and Brotherhood, which were secret societies who date back years into PB's past. She figured out that these societies had something to do with what happened to Grace, and so she goes digging for information. She finds secret tunnels all the way under the school, and with her friends Liam and Seth, she explores the tunnels and finds lots of useful information. So, when she confronts the societies, there is a fight, and the police are called. But, Kate's evidence (invitations to join, etc) is then destroyed by the police who obviously are also working with the societies. So Kate goes to see the old librarian, who says that she can never give up, so the book ends with Kate deciding to find more evidence to prove that Grace's death wasn't an accident.
If you feel like I've missed anything, comment below and I'll add it in! Thanks :)