Marcy was a resident at the hospital Liv worked before she became a zombie. She is identifiable by her grandmother's pearl necklace that she always wore.
In Pilot, Marcy worked alongside Liv Moore in the E.R. in the first scene. She was impressed by Liv's quick thinking and bold save. When they both got off shift, Marcy caught up to Liv and told her that although they should be rivals, she kinda likes her, implying a frenemy relationship. Liv is surprised because she thought Marcy hated her. Marcy then invites Liv to the boat party on Lake Washington that night. When Liv at first declined, Marcy told her she should show everyone she's "not an over-achieving pain in the ass." Liv declined again because she had plans with her fiancé, Major Lilywhite, with whom she immediately leaves. Marcy called after them and said that Liv's life is basically the ending of 16 Candles. Liv does eventually join Marcy at the boat party after being convinced by Major, where both Marcy and Liv are turned into zombies. After the Lake Washington Massacre, Marcy is missing and presumed dead, so Liv attends her empty-casket funeral where she sees Marcy's mother weeping.
In The Exterminator, Marcy was found by Liv and Ravi. She had been trapped in a hole in an abandoned shipyard on the shore of Lake Washington. Two teens who were filming stumbled upon her and posted a photo of her, claiming she was a zombie. Ravi found the picture by setting up a Google Alert for the search terms "Seattle, zombie" as a way of having an early warning system. When Ravi and Liv went to find her, she was a deteriorated Romero due to months of starvation. Liv identified her as Marcy by her pearls. Ravi hoped that he could reverse her transformation by feeding her brains and other organs. Once Ravi threw them down, she eagerly began eating, and Ravi and Liv left. When Ravi and Liv returned, she was still a Romero because she was too far gone. Ravi wanted to keep trying but Liv said they had to kill "it" in a deadpan voice due to her brain of the day. Despite this, Ravi attempted to collect a sample from Marcy with a syringe attached to a long pole. This agitated Marcy, who grabbed the pole and caused Ravi to fall in the hole. She tried to attack him but Liv jumped in and killed Marcy with a pipe, saving Ravi despite her apathetic brain. Ravi and Liv collected Marcy's body and presumably burned it. Beforehand, Liv took Marcy's pearl necklace off her body. Liv then returned the pearls to Marcy's mother. Marcy is the first person Liv kills in the series.
- Olivia Moore: Marcy worked at the same hospital Olivia did in Seattle, and had a slight rivalry with her. Marcy, however, came to respect Olivia and invited her to the fateful boat party.