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Intro. Arthur Mitchell, often referred to as the "Trinity Killer," is a fictional character and the main antagonist of the fourth season of the Showtime TV series Dexter. Mitchell is a serial killer who presents himself as an unassuming church deacon, high school teacher and family man. He kills to suppress his childhood trauma of accidentally causing his sisters death, and ruining his family. FBI agent Frank Lundy (Keith Carradine) dubs him the "Trinity Killer" because of a recurring pattern of three killings based on traumatic events during Arthur's childhood.

Arthur Mitchell

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