Dead ringer - Lisa Scottoline

Ace lawyer Bennie Rosato is duelling evil in the form of her own twin sister, ex-convict Alice Connolly, who has returned to Philadelphia to exact her revenge and ruin Bennie. At the same time, Bennie's law firm is in trouble, so she takes on a potentially lucrative class action suit to save the day. Meanwhile, her colleague Mary DiNunzio persists in bringing in a case that will just provide more headaches - and laughs - than dollars. But then a mysterious stranger appears just in time to help Bennie in the fight of her life - a fight that turns out to be for her life.