Introduction & Events
Margaret was the maternal aunt of Claire La Foret (the film's main protagonist) and the sister of her mother Jean, who died years prior in what appeared to be an accidental drowning on Christmas. Margaret's backstory also revealed that she divorced her husband Dirk, after learning he had had an affair with Natasha, the daughter of Margaret's brother Stuart and Margaret's niece. This left Margaret at odds with both Natasha and Stuart, resenting the latter for squandering her savings in bad stock market investments.
The film's events had the La Foret family invited to the cabin by Claire's grandfather and Jean's father, leading to quick tension when Margaret learned that Stuart had brought Natasha to the gathering. Margaret was also angered when she learned that her father had planned a game to determine who would inherit his fortune when he ultimately succumbed to his cancer, citing how Jean had always hated them. Margaret's alcoholism was shown in full display during the gathering, leading her to reject Natasha's attempt to apologize for her past actions. Margaret's rejection caused Natasha to snap at her and claim her bad temper was what drove Dirk away, later retaliating against Margaret by shoving her off a balcony while she was trying to grab a decorative star (believing it to be a clue for the game).
While it appeared that her grandfather had died shortly after announcing the game's commencement, Claire soon learned the truth: her grandfather had conspired with his assistant Sergio Boniti to fake his own death, as the true purpose of the gathering and game was to figured out who killed Jean, as he firmly believed her death wasn't an accident and that someone in the family killed her. Having already found a note from someone trying to get her grandfather to stop the game, Claire began investigating with her grandfather and saw via hidden security camera footage her friend Monica retrieving the murder weapon from the crawlspace, leading her grandfather to believe Claire's brother Ian was responsible for Jean's murder and Monica was covering for him.
But after confronting Monica and Ian, Claire saw that Monica had been slipped a note by the true killer, informing her of the location of the murder weapon (which was wrapped in a towel) and making it appear to be written by Ian. Claire unwrapped the murder weapon to reveal it to be a silver candlestick, with Claire remembering that Margaret had tried to slip it into her bag when she first arrived at the cabin. This served as the reveal that Margaret was Jean's killer, and Claire went to confront her in the nursery when she realized that would be where her aunt would be. After realizing she was caught, the distraught Margaret apologized for ruining Christmas before revealing she was wielding the pistol from her brother-in-law's office, responding to her niece's pleas to give her the gun by saying she hadn't meant to kill Jean and that she couldn't live with the guilt anymore.
As for her motivation, Margaret revealed that she had begun stealing from Jean, citing that she only did so out of desperation and that she believed Jean had more than enough money. On the day of her murder, Jean was confronting Margaret for having stolen one of her silver candlesticks, being especially angry after having gotten into a fight with Ian. Jean continued to berate Margaret even as she attempted to return what she'd taken, driving Margaret to swing the candlestick at Jean. The swing caused Jean to fall and strike her head on a rock, killing her instantly. Panicked and drunk, Margaret covered her tracks by leaving Jean's body near the lake to make it appear she died in an accident, taking Jean's necklace out of a belief that she deserved it. Later on, though, Margaret would sell the necklace out of a desperate need for money after her divorce and Stuart losing her money, thus leading her father to realize Margaret was Jean's killer.
After her tearful confession to Jean's murder, as well as blasting her father's ploy to make her confess as "mean", Margaret pointed the gun at herself and revealed she intended to commit suicide, feeling extreme remorse for her actions. But after Claire revealed that the gun was actually a prop her grandfather was using in his game, Margaret bemoaned how she couldn't even kill herself properly before breaking down in tears as Claire comforted her. Later on, the police arrived and took Margaret into custody, with her father later revealing she was going to be institutionalized and receive psychiatric help.
- Nola Augustson later appeared on Ransom as villainous conspirator Lydia Marsh.