(Capcom's primary storyline)
"I'll feed you to my babies and fertilize the garden with what was left."
Marguerite was the matriarch of the Baker family, which consisted of her husband, Jack, and children, Lucas and Zoe. They lived on a large plantation in the Louisiana swamps, comprising a mansion and an older house, with mines and a pier nearby.
In 2014, the Baker family encountered Mia Winters and Eveline, who had been washed ashore after being shipwrecked, and decided to take them in. Unbeknownst to them, Eveline was a bio-organic weapon who possessed telepathic powers and was obsessed with having a family of her own.
Under Eveline's influence
"You're gonna have a little sister, Zoe!"
— Marguerite searches for Zoe in the middle of the night.
Eveline slowly infected both Mia and the Baker family with her mold. Marguerite consulted a doctor, who advised her to come back for further testing, as they had found mold on her skull during an x-ray. She planned to return to the doctor, but Eveline's infection would consume her before she could, and the newly possessed Marguerite would now view her infection as a "gift". She hid a D-Series Arm in Eveline's room to keep it safe, as it could be manufactured as a serum to eliminate the "gift" in a victim's body.
As a result of the infection, Marguerite gained the ability to produce and control mutant insects that hatched from Eveline's mold.
As the infection's hold over them strengthened, the family withdrew from community life completely, causing the locals to declare them dead and label sightings of the infected family members as supernatural phenomena. In actuality, Marguerite and her family were capturing people and turning them into Molded, which would add to the "family" Eveline wanted. They kept a list of the people they killed and turned, as well as newspapers reporting the dramatic increase in disappearances.
The family also turned to cannibalism, with most of the food Marguerite cooked being human body parts harvested from their victims. Zoe fled the house and hid out in the family trailer, where she guided kidnapped victims to escape. Marguerite and the family were aware of her "betrayal", however, and began antagonizing her.
In June 2017, three years after the arrival of Eveline, the American TV paranormal investigation series Sewer Gators investigated the house as a possible episode, resulting in the murders of producer Andre Stickland and presenter Peter Walken. The crew's cameraman, Clancy Jarvis, was shackled to the bed in Jack and Marguerite's bedroom while Marguerite welcomed him and forced him to eat their food, planning for him to join their "family". While she was not present in the room, Clancy uncovered various puzzles which he would need to solve to make his escape, but in the process caused loud noises that forced him to return to the bed as the Baker matriarch returned.
Marguerite would bring more food and would become more antsy as Clancy refused to eat the food. Eventually, Marguerite returned to the bedroom just as Clancy was about to escape, leading him to lunge at her and stab her in the throat, which incapacitated her and allowed him to evade capture.
"Rise and shine, sleepyhead. It's time for supper."
— Marguerite welcomes a now conscious Ethan to dinner.
Ethan Winters, Mia's husband, arrived at the Baker house a month after the incident with the Sewer Gators in response to an email he had received from Mia under the control of Eveline. Some time after Ethan and Mia reunited and were both captured by Jack, Mia escaped captivity and recorded a message for Ethan while she attempted to flee from a pursuing Marguerite, who was also aware of Zoe's collusion in her escape attempts. The chase led into a crawlspace in the old house, where Margureite would corner Mia and capture her.
Marguerite would then prepare a meal of various human meats for the Baker family, as well as their "guest" Ethan in an attempt to "welcome" him into their lifestyle. However, after Ethan rejected and spat out the food upon Jack trying to force feed it to him, Marguerite became shocked and panicked, causing Jack to snap at her and force her to leave which she did so, visibly angry and upset, and screaming manically that he isn't eating his food. 
When Ethan entered the second house in search of the D-Series Arm which could create the serum, Marguerite encountered him once again, continually attacking him with her bugs as she stalked him throughout the old house. Eventually, she halted Ethan's progress to the second floor and trapped him in a deep hole where she sent her insects to attack him, but he was able to fight off the insects and wound her enough to cause her to fall into the hole. She desperately clung to her lantern, however, as she was enveloped in a pool of insects.
Final confrontation with Ethan and death
"Come on now with me. We're going to settle this."
— Marguerite attacks Ethan in the greenhouse.
Ethan did not get far from the encounter before realizing that he needed Marguerite's lantern to progress further on the second floor. Upon returning to the hole, however, he witnessed an elongated arm belonging to the now mutated Marguerite snatch the lantern away through a small underground passage, which would lead to her taking refuge in a greenhouse. After Ethan followed and confronted her in the greenhouse, he finally dealt the killing blow to Marguerite, causing her to calcify and leave behind her lantern.
Marguerite's death also marked the deaths of all of her insects. Jack would later learn about Marguerite's death, and while fighting Ethan at the boat house proceeded to sob and call out her name. While Ethan was cocooned later by Eveline, he saw a vision of Jack, who reveals that his family, including Marguerite, have all fallen victim from Eveline's mind control. He then pled with Ethan to "free" his family from Eveline. After Ethan killed Eveline, he acknowledged that the Baker family were simply victims of Eveline's possession - as much victims as he and Mia were.
Marguerite was once a caring, loving, dutiful, kind, and traditional aged housewife who became twisted under Eveline's "gift", becoming a demented, sadistic, insane, and psychopathic shell of her former self. Even when she initially became infected by Eveline's gift, she showed some hints at her prior nature, where she tells Zoe to come out of hiding in a gentle manner to meet Eveline (a noticeable contrast with her treatment of Mia in a similar situation later on where she was very hostile even when she tries to find her), and will noticeably hesitate to harm Zoe and even fight off Eveline's control long enough for Marguerite to give Zoe a key to the family car so the latter can find help.
Marguerite still attempts to treat her "guests" with care, only to serve up human organs and Eveline's corrupting gift as meals. When her food is refused or she is challenged in general her sweet facade drops, revealing a violent and unhinged individual who threatens in the most disturbing ways imaginable. In some cases, she even reacts violently towards an individual simply to take her anger out for an unrelated event. This was best demonstrated during the Bedroom DLC where she marches into Clancy's "bedroom" and proceeds to repeatedly stab him almost to death due to extreme anger from an argument with Jack Baker, only stopping when the latter arrived to apologize for his earlier behavior.
Marguerite lives in a delusion where she is convinced she is being the best she can be, and as such cannot understand why her precious guests refuse to eat or constantly try to escape. This only worsens her rage, complete with psychotic fits as she hunted for Mia while screaming about the ungratefulness of her guests.
In the latter stages of her illness as she began to embrace Eveline's "Gift", Marguerite began to adopt a darkly religious and fanatical outlook in private affairs, making a "shrine" out of the D-series cranium briefcase, accepting the D-series arm from Eveline as a "gift of fortune" and threatening horrible retribution on anyone who dared to touch these gifts, even her own daughter.
She also seems to have a huge fondness for bugs, at least post-infection, to the extent that she takes offense at anyone using phrases that infer bugs get hurt. This is implied by Jack Baker when, while stating his intentions to "squish [Ethan] like a bug", he then worries about whether Marguerite heard him say that.
Out of all of the Baker family members, she is the most visibly inhuman upon receiving Eveline's "gift", sporting demonic eyes and gaining the ability to control mutant insects. Belying her frail appearance, Marguerite possesses superhuman strength and speed. Her speed is demonstrated by her hunting down an escaping Mia Winters: Upon detecting Mia, she is capable of outrunning her, and also proceeds to lift her up by the neck, and later dragging Mia by the legs with minimal effort in the crawlspace at the end of the video. She also demonstrated a similar speed burst when, after she discovered Clancy was missing from the bed, rushed into the nearby room and proceeded to lift him up, although Clancy temporarily stunned her by stabbing her in the neck.
Like the rest of the Baker family, she possesses the ability to regenerate from damage, although she is far from invincible. When stabbed by Clancy, she only reacts with irritation, although she does struggle in trying to get the knife out of her. When severely wounded by Ethan, she is covered by a strange liquid that damages Ethan's health and later appears in a greenhouse with massively enlarged limbs. In this state, she gained the ability to crawl along walls like an insect and would use this ability to ambush Ethan. More disturbingly, her lower abdomen becomes a swollen insect hive which she could use to discharge swarms toward Ethan, but would cause considerable pain to her if Ethan successfully damages it. Even prior to her transformation, however, she can emit a centipede-like creature from her mouth. She demonstrated this first to Zoe in an attempt to show off Eveline's "gift", and later if she catches Clancy out of bed.
- kaitaishinsho, p.009.
- Marguerite's Notebook
- Resident Evil 7 Teaser Demo: Beginning Hour