pretty little liars

In the first book Ali, Hannah, Aria, Spencer and Emily are seventh grade best friends. They are "the clique" to be in at school, and for the end of seventh grade they decide to have a slumber party. Little did they know that that night would be the start of all their problems. After school on the last day Hannah, Aria, Spencer and Emily go to Ali's house to surprise her with the plans for their "super slumber party" but once they were there they felt a strange vibe coming from her house when Ali's mom yelled at her for no reason. But no one payed much attention to it.