It's been a year since Alison disappeared, but she's been present in her friends' minds ever since. She was their Queen Bee and the most popular girl in school. Manipulative and vindicative, Alison knew everybody's secrets. Since she's been gone, her friends are beginning to realize how little they really knew about her — though they do seem to know more about her mysterious disappearance than they're letting on. Now the girls are getting strange messages from "A" — messages that include info only Alison would know. They also catch glimpses of someone who looks exactly like Alison. But it can't be Alison. Can it?