A girl's guide to murder...

Five years ago, a tragic murder-suicide rocked the small town of Little Kilton, Buckinghamshire[nb 1] when popular schoolgirl Andie Bell was brutally murdered and her boyfriend, Sal Singh, was accused before seemingly taking his own life. While at first Sal was just a person of interest, he later became named the killer because of a confession text he allegedly sent. But seventeen-year-old Pippa is convinced that the real killer is still out there. She befriends Sal's younger brother, Ravi, and launches an investigation under the disguise of a school project. Unfortunately for Pip, each interrogation puts Pip in greater danger, yet she still persists. She finds evidence that Andie was selling drugs to students, including Max Hastings, and was having an affair with Mr. Ward, history teacher and father of Cara Ward, Pippa's longstanding best friend.

Pippa finds out Mr. Ward pushed Andie into a desk in a moment of fury. When Andie went missing, Mr. Ward thought he had killed her, so he framed Sal and murdered him while making it look like a suicide. A few days later, Mr. Ward saw a girl walking through the street and mistook her for Andie. Pippa discovers that the girl wasn't Andie, but a girl that looked like Andie. Becca, Andie's sister, confesses that Max Hastings had drugged and raped her - with rohypnol sold to him by Andie. In anger, Becca pushed Andie, who fell, convulsed and died. While still in shock, Becca takes Andie's body and hides it in an old septic tank in a farmhouse near Pip's home. When Pip learns of the truth and goes to confront Becca, she is drugged with rohypnol and Becca tries to choke her to death. That doesn't happen as Ravi comes to save her.