The Ninth Key (The Mediator, 2) by Jenny Carroll
Reading level: Young Adult
"There's no such thing as ghosts". At least, that's what the scientific community believes. High school sophomore Susannah Simon wishes she could agree. She's only lived in sunny California for two weeks, and already her life's a whirlwind of pool parties, excellent hair days, and new friends. Oh, yeah ... and her stepbrothers. But otherwise, things are going fab. Until the ghost of a dead woman shows up at her bedside, screaming and begging Suze to find "Red" and tell him that he isn't responsible for her death.
Buy The Ninth Key (The Mediator, 2)
Tracking down a murderer isn't exactly easy, especially when the clues that Suze pieces together lead straight to the father of Tad Beaumont, the cutest and richest boy in school ... and the first boy who's ever asked Suze out. Oops.