Disciple

A murder victim bears an exact resemblance to Lanie. Investigation soon leads to another victim who resembles Esposito. The only connection between the two victims is plastic surgeon Dr. Kelly Nieman (Annie Wersching), who apparently has no motive. Castle believes this has something to do with Jerry Tyson—better known as the Triple Killer—whom everyone but himself believes to be dead. The team discovers too late that the Lanie and Esposito doubles were used to destroy all evidence of Tyson's crimes before they were murdered by his acolytes. Nieman escapes before she can be apprehended, leaving behind a flash drive intended for Castle and Beckett. Its seemingly innocuous contents leave Beckett deeply disturbed.