Born in Louisville, KY, Carpenter began acting at an early age, playing Tiny Tim in her hometown's annual Dickens on Main Street festival when she was eight years old - a role she held on to for three years. She was next spotted by Jon Jory, then-artistic director of the Actors Theatre, who cast her in several plays, including "Trudy Blue." From there, Carpenter attended Sacred Heart Academy while joining Louisville's Walden Theatre, where she excelled in several performances, including as Helena, Shakespeare's sensitive and lovesick maiden who develops into a happy and confident woman in "A Midsummer Night's Dream." Her exceptional gifts and string of strong performances throughout her adolescence allowed Carpenter to enter the prestigious Juilliard School in New York City, an intimidating move for the young Southern girl.Carpenter spent three years honing her craft at Juilliard, but left before graduating to appear in an off-Broadway production of Richard Greenberg's "Everett Beekin," opposite Robin Bartlett and Bebe Neuwirth. She moved on to Broadway proper with a co-starring role opposite Liam Neeson and Laura Linney in "The Crucible," Arthur Miller's play about the Salem Witch trials that served as a metaphor for the Red Scare of the early 1950s. After auditioning four times, Carpenter was awarded the role of Mary Warren, a lonely girl who takes over as the Proctor's housemaid and eventually accuses her abusive employer (Neeson) of witchcraft. Graduating to features, she had a small role in "White Chicks" (2004), then co-starred in "The Exorcism of Emily Rose" (2005), giving a powerful and memorable performance as a young college student who believes she's possessed by demons, but dies when her priest (Tom Wilkinson) performs an exorcism on her. She earned critical acclaim from all circles and even won Best Frightened Performance at the 2006 MTV Movie Awards.While a prominent film career was definitely in the making, Carpenter instead jumped over to television for a regular series role in "Dexter" (Showtime, 2006-13), the cable station's darkly humorous procedural about Dexter Morgan (Michael C. Hall), a blood spatter specialist for the Miami Police Department who also happens to be a serial killer, though one with strict guidelines to kill others who have escaped justice. Carpenter played Debra Morgan, Dexter's foul-mouthed sister and homicide detective in the same police station. In her first audition, Carpenter connected with her future character by struggling with a line and blurting out frustrated profanities, leaving no doubt in the producers' minds who was going to play the part. On the show, her character suffers from being insecure about her adopted brother's close relationship with her father, Harry (James Remar), who took the boy in after finding him on a gruesome murder scene when he was three. But the bond between brother and sister remains tight throughout, even though she has not a clue about his extracurricular activities. Carpenter's character was quickly a fan favorite on what became Showtime's most popular series. Back in features, Carpenter appeared in the ensemble drama, "Battle in Seattle" (2008), then starred as a Los Angeles-based reporter who finds herself trapped in an apartment complex plagued by a strange disease in "Quarantine" (2008).