Mary Leyendecker is the sister of Scarlet Leyendecker.
Mary was visiting her sister, Scarlet, when Scarlet's new boyfriend came in. She asked him if he was one of the good ones and he said he liked to think he was. Mary said Scarlet had been waiting for a long time for a good one. They had dinner together, where Mary said Ronald seemed like a nice guy, but that she thought she recognized him from somewhere.
Mary later return to Scarlet's, concerned about Ronald. Scarlet brushed off her concerns, but their conversation was quickly interrupted by Ronald, who overheard them talking. Mary tried to get a picture of Ronald, but he refused, citing concerns about deep fakes, until she got into the picture with him. He forced her to pose between himself and Scarlet, then told her they say when three people take a picture together, the one in the middle dies first. Mary later texted Scarlet to tell her not to trust Ronald, but was unaware that Ronald had stolen Scarlet's phone.
Ronald went to Mary's house, using his taser to force his way in. He wrapped her up in a blanket and sealed it closed. Then he asked her about her intentions. When he cut a slit in the blanket so she could talk, she claimed she didn't tell anyone else, even when he threatened Phoebe and Scarlet. He checked her search results, which showed that she'd looked for Dewell & Hoyt Private Investigations. She claimed no one answered and she just left a voicemail asking them to call her back. Then she called Ronald a monster. When she wouldn't stop saying it, he started stabbing her. He later cleaned her house up and took her body away in his truck. He later buried her body in the woods.
She and her sister grew up in Utah. Their father was a member of a splinter LDS group. As an adult, she had no contact with her family except her sister.