Mary: The Angel of Mercy, A Lethal Nurse

Character Profile
Portrayed By
Denise Crosby
Season One
First Appearance
Popping Cherry
Last Appearance
Popping Cherry
Appears in
One Episode
Full Name

Manner of Death
Killed by Dexter Morgan on Harry Morgan's orders
45 (at death)
Personal Status
Marital Status

Professional Status
Killer Profile
"No Known Moniker"
Number of Victims
At least 5
Modus Operandi
Killing Method
She Injected victims with overdoses of an unknown drug mixed with morphine, causing them to die. She then collected their obituaries as trophies in a scrapbook.
Method of Disposal
None. Mary left her victims where they died.
Mary killed under the excuse that she was taking away her victims' pain.
""A body cannot suffer in sweet repose." - Mary, to Debra"

Mary (also referred to as "First Nurse") was a character on Showtime's series DEXTER.

She was an "Angel of Mercy" serial killer working as a nurse at a time when Harry Morgan was hospitalized. She was poisoning him with lethal amounts of morphine. As a result, she became Dexter Morgan's first human victim.


Mary killed patients under the delusion that she was "taking their pain away." In 1991, when she tried to kill Dexter Morgan's bedridden father, Harry Morgan. Dexter was given instructions by Harry to kill her.


While Harry Morgan was being treated in a hospital, he realized that his nurse, Mary, was in fact an Angel of Death who was killing him slowly by overdosing him with morphine as well as another unidentified substance. He gave Dexter Morgan the go-ahead to kill her in order to stop her from killing him and any more people.

Dexter broke into Mary's house and covered a room with plastic. He donned a full plastic suit with gloves. (Casual clothes were worn underneath.) He waited for Mary to arrive as he held a syringe (which was ironic because Mary herself killed via syringe). Dexter failed to sedate her in this way, though, and was forced to overpower her in hand-to-hand combat. After he stripped Mary of her clothes, he covered her in shrink wrap and secured her to a table with duct tape.

When Mary awoke, Dexter reminded her of her crimes (via her special trophies scrapbook, where she kept obituaries of her victims). Mary claimed that she helped them by putting them out of their misery. However, Dexter threw her words right back at her by stating that he was going to take her pain away.

Dexter gagged Mary again and repeatedly stabbed her, which was quite messy with her blood spraying onto him. He then dismembered her by hacksaw and tossed her remains into the Everglades.

Dexter's intervention prolonged Harry's life another year before he died.


Since Dexter did not take a blood slide from her or dispose in the Underwater Graveyard, the police never knew that she was a Bay Harbor Butcher victim. An investigation into her disappearance was never mentioned, and it is unknown if the police ever discovered her crimes.


  • Other victims - In her apartment, she had a scrapbook with obituaries of her victims. As Dexter browsed through it, four obituaries were seen in the middle of the scrapbook. It likely contained many more obituaries

Attempted Victim

  • Harry Morgan - Mary tried to poison him with an unknown drug mixed with morphine, but he caught onto what she was doing. Harry told her to stop, which made her angry. He then sent his son to kill her as practice in killing more people like her.


"The nurse was my first playmate. I'll always be grateful to her for opening up so many magnificent new doors for me. Things were a little messy in the beginning. Hey, perfecting a new craft takes time. But I was trained well. Those who witnessed my early stumbles never had a chance to tell." ~Dexter


  • She had a black cat, named Mr. Tinker.
  • Mary's last name was never revealed. In the original novels, her first name is also absent. She was referred to as First Nurse.
  • Mary was Dexter's first female kill shown in the series.
  • Denise Crosby also played a character with the same name in The Walking Dead


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