Mary (Dexter)

"The body cannot suffer in sweet repose"

- Mary's justification for killing patients

Mary (referred to as First Nurse in the novels) is a minor, yet pivotal antagonist in Showtime's Dexter. She is a nurse who ultimately completes Dexter Morgan's transformation into a serial killer.

She was portrayed by Denise Crosby, who also portrayed Rachel Creed in the 1989 adaptation of Pet Semetary.

Biography
When Dexter's adoptive father Harry was in hospital he realised that a nurse named Mary was trying to kill him by giving him a morphine overdose and gave Dexter the go-ahead to kill her as part of his "training" to kill people who deserve it. Dexter broke into her house and covered everything with plastic, however he failed to sedate her and had to beat her up. He then confronted her with a scrapbook containing the obituaries of all her victims (although only four are shown, it likely contained many others). Mary defended herself, claiming that she was taking her victim's pain away, however Dexter simply replied that he was going to take her pain away. Dexter then gagged Mary and repeatedly stabbed her, causing her blood to spray everywhere.

Trivia

 * Mary is Dexter's first female victim, as well as his first ever victim (chronologically, in the show his first victim was Mike Donovan)
 * She is never named in the book, being referred to as First Nurse.
 * Two of her victims are named Adam Horrocks.