R.S.V.P. murder

While mourning the death of her father, once a celebrated, brilliant criminal lawyer, Frances Hilliard learns that he tried to ensure her future financial security by means of an unusual but potentially lucrative method - blackmailing former clients about whom he knew far too much. The proofs are contained in his missing diary, a diary that one of his victims decides must still be in Frances' possession. The week before his death, her father had her mail five letters, but which one was sent to a murderer?