context: England, 1921. Florence Cathcart (Rebecca Hall) is a published author on supernatural hoaxes who works with the police to expose charlatans and debunk supernatural phenomena. It's revealed she lost her lover in the war, and every ghost "hunt" is an attempt to see if it's possible to bring him back. Every time she proves a hoax, the truth and pain hit her again. She receives a visit from Robert Mallory (Dominic West), a teacher from a boys boarding school in Cumbria. Robert explains to her that there have been sightings of the ghost of a child at the school, and that it may have been the cause of the recent death of a pupil there. Robert asks Florence for help to figure out why the supernatural events occur. Although Florence originally refuses, Robert's concern for the orphaned kids at the school causes her to change her mind since she is an orphan herself. Florence travels to the school, which was a stately home until 20 years earlier, to investigate the sightings and the recent death. She is welcomed by Maud (Imelda Staunton), the school's housekeeper and matron, who tells Florence that she has read her books and feels like she knows her. After investigation, the ghostly sightings are thought to be a prank led by two boys who have been bullying a lonely, redheaded boy into doing what they want for their approval. With regards to the recent death, Florence deduces that one of the teachers was the last person to see the boy alive and questions him, until he admits to making the young boy stand outside to "man up", after he claimed to have seen the ghost, thus scaring the young boy and causing him to have a fatal asthma attack. The school then closes for half-term with the only occupants being Florence, Robert, Maud and Tom (Isaac Hempstead-Wright), a lonely boy who tells Florence his parents live in India.
  Her job seemingly done, Florence prepares to leave. Down at the lake she drops her cigarette case, which belonged to her dead boyfriend. As she reaches for it, a hand reaches for her from the water. She steadies herself and then falls into the lake. She is rescued by Robert but he and Maud are concerned about her mental stability. Florence recovers but starts seeing and hearing more unexplained things, which prompts her to stay at the school. After chasing what she believes is the ghost, she sees an apparition of a man with a shotgun, who appears to shoot her. She also keeps hearing a child's voice calling "Mowzy", which she tells Tom was the name some Africans gave to her, after she was rescued from a lion attack as a child. Florence and Robert start developing a mutual attraction but Edward Judd (Joseph Mawle), the grounds keeper who has a grudge against Robert for being a war hero, is jealous and attempts to rape Florence in the woods. Florence, assisted by a supernatural apparition, accidentally kills Judd in self-defense. She stumbles back to the school and tells Robert, who then goes out to bury Judd and cover up the incident. Florence tells Robert not to tell Tom about what happened as it will upset him but Robert tells her that there are no children at the school at the moment.
  Florence realizes that Tom is the ghost that is haunting the school. With this revelation, buried memories begin to surface in Florence. The stately home that is now the boarding school was once Florence's family home where she lived as a child. It was the place where she watched her deranged father murder her mother with a shotgun and then tried to kill her too. As a child, Florence ran into the hidden passages in the walls of the house where she used to play but her father pursued her calling out for his "little mowzy". Aiming for her, her father then accidentally killed Tom, who was revealed to be her father's illegitimate son and Florence's half brother. Her father then killed himself while Florence watched. Maud is Tom's mother, and was Florence's childhood nanny. Due to the intense trauma, Florence had blocked these childhood memories, including her memories of Maud, instead inventing new memories such as a childhood in Africa. After regaining her memory of her childhood, Florence converses with Robert about how he can also see the ghosts (his past war buddies who had died in battle). It becomes apparent that those who are very lonely or haunted by the past can see spirits. Maud, who also sees Tom's ghost, explains that Tom is lonely and that he needs his family, which is why she arranged for Florence to come to the school in the first place. Maud poisons herself and Florence, intending for their ghosts to join Tom. Maud tells Florence that the lonely children at school are starting to see Tom. Florence tells Tom that her soul will not rest if she dies now but that she will always be with him. Tom then helps Florence by bringing her medicine to throw up the poison, Robert comes back and sees the spent bottle lying next to Florence on the floor. The following scene shows Florence walking throughout the building, about to leave the premises with Robert. She passes by several adults on her way out but none notice her, even when she walks directly in front of them. One man even speaks badly of her after she passes right in front of him. Then the redheaded boy finally acknowledges her. Florence catches up to Robert and shares a cigarette with him as they chat. Florence explains how not being able to see the ghosts anymore is not the same as forgetting them. She asks Robert to tell the driver to pull up to the end of the drive since she enjoys the long walk and that she will see him on Saturday. The couple exchange a kiss and Robert watches her walk away as she says hello to several other children along the path.
  In an interview with director Nick Murphy, he has confirmed the status of Florence at the end of the movie, "This film is about people seeing what they need to and seeing what they need to is carrying forth of the film and as such, I wanted to give audiences that chance at the end. Yeah, I know what she is. Rebecca and I decided sheâs alive and then she smokes and she gets a car." [2]
question: Who killed Florance's mother?
answer: Her father