Afteraharddayofvolleyballatthebeach,ateenwhoseparentsareawaydecidestohaveaslumberpartywithhergirlfriends.Theirboyfriendspredictablyshowuptoscarethem,butastrangerfromthebeachisalsoseenlurkingaroundthehouse.Soonthegroupbeginsexperiencinganattritionproblem.