** spoiler alert ** I love this series in general but this is my favorite one so far. the girls have been receiving texts from this person called "a". all of them assumed it was alison who was murdered during a sleep over. also they assumed it was alison because they only told alison their secrets. alison thought that that was what made friends closer. these girls found something creepy so they decided to come together and find out who "a" was. in the previous book, hanna was hiding and saw who "a" was. She was trying to tell someone when she got into an accident. they girls starts to think it was melissa who killed alison. when Emily and Hanna were chating and something emily said had made hanna's mind go off. she had remembered who "a" was! meanwhile, Mona and spencer decided to go to the cops and tell them that melissa did it but then Mona drove into a mountian sort thing. when she tried to push spencer off the cliff, spencer moved leading to mona's death.