"Pretty Little Liars" is a series of novels for young adults written by Sara Shepard. The books concern the lives of a group of school friends after the leader of their social clique, Alison, disappears. The girls start receiving messages from someone calling themselves "A" who threatens to reveal their secrets. "Wanted" is the eighth book in the "Pretty Little Liars" series and was first released in 2010.
A press conference is held to announce the discovery of Alison's twin, Courtney. The four friends -- Hanna, Aria, Emily and Spencer -- are shocked by this and believe it means Alison must still be alive. Courtney goes back to live with her parents and slowly begins to start friendships with Alison's old friends. Eventually, she reveals that she is actually Alison and she and Courtney swapped identities on the night that "Alison" disappeared.
Alison goes on to claim that her family never believed her story, as Courtney was notorious for pretending to be Alison, so they sent her to live in an insane asylum. The four girls and Alison visit a school dance together to celebrate her return. However, on the way there Spencer receives a phone call telling her that her sister Melissa has gone missing. In the ensuing confusion, it's revealed that the girl the four were friends with all those years ago was actually Courtney, and the girl they're with now is the real Alison, who killed her twin.
Alison sets fire to a house in an attempt to kill the four girls. The four girls manage to escape from the house, freeing the kidnapped Melissa in the process. Alison is trapped inside the house; the police assume she has died, although no body is ever discovered. It's confirmed that Alison killed Courtney and was also "A": she targeted the four girls because they were part of Courtney's life that was denied to her.
Hanna's mother comes back to her hometown and kicks her father out of the house. Hanna and Aria both get back with their former boyfriends, Mike and Noel. Spencer's father apologizes for his mistakes in the past and promises he's going to be a better father from now on. The book ends with Emily burying possessions belong to Alison at Courtney's grave, but she can't be quite sure if the noises she hears at the cemetery are just animal sounds or something else...