Heather's given name is Cheryl Mason, the adopted daughter of the writer Harry Mason, who survived the events of the first Silent Hill game. When Harry escaped Silent Hill, Alessa, the Incubator, came back as an apparition and presented him with a newborn baby, which is both Cheryl and Alessa herself restored to one body again. Harry left Silent Hill with the baby and moved to Portland.
Harry was unsure about raising the baby, and considered killing, strangling and abandoning her because he suspected the baby was a reincarnation of Alessa, and Alessa was responsible for taking Cheryl away from him. However, Harry decided to raise her. Harry decided to name the baby Cheryl again. However, he later felt this name was a mistake since at the time, Harry only thought of her only as a replacement for his lost Cheryl.
Five years later, they were attacked by a member of the Order in Portland and Harry killed him in self-defense. In an attempt to throw the cult off if they come and look for them, he renamed her Heather, dyed her hair blonde and relocated to another city. Harry eventually settled in the Daisy Villa Apartments with Heather.
On one of Heather's birthdays, Harry gave her a pendant with a red jewel inside and told her to take good care of it and to never take it off; the reason being that the red jewel is crystallized Aglaophotis which can expel demons, so if Heather should ever be in danger of birthing the Order's god again, she could survive by swallowing the Aglaophotis and expelling God.
When Harry fights and defeats the Incubus, and the Incubator gives him a baby (who is revealed to be Heather Mason in Silent Hill 3) and shows him the escape route. Harry, Cybil, and Kaufmann try to escape, but a blood-covered Lisa Garland appears and drags Kaufmann with her into the abyss. Harry and Cybil continue their escape; however, the Otherworld is collapsing too quickly for them to make it on their own, so the Incubator uses the last of her power to stop the world's destruction in order for them to escape. The Incubator is then consumed by the flames and Cybil and Harry escape together with the baby.
Silent Hill 3
While running an errand for her father at the Central Square Shopping Center, Heather accidentally falls asleep and dreams about Silent Hill. She finds herself wandering through the nightmare version of Lakeside Amusement Park. While she is walking along a roller coaster track, she is struck by a roller coaster.
When Heather awakens from the nightmare, she exits the fast food restaurant she was sleeping in and calls her father, letting him know that she is on her way home. However, when Heather is about to leave the mall, a detective named Douglas Cartland attempts to talk to her about her birth. Heather, thinking Douglas a stalker, flees him and exits the shopping mall through a bathroom window to avoid confrontation. However, the alley past the window is blocked, and she is forced to enter the shopping mall again through the employee's area. Heather finds a monster and manages to kill it with a handgun, shaken by the sudden realization that monsters exist.
As Heather wanders through the monster infested mall, she encounters a barefoot woman in a black dress with flowing platinum blonde hair who reveals herself as Claudia Wolf. Claudia tells her about a paradise created by God and Heather's "true" self. Heather is confused and comes down with a serious migraine as Claudia departs, as if she is trying to remember something from long ago.
While descending an elevator, Heather soon plunges into the Otherworld version of the shopping mall. She tries to convince herself that everything is just a dream. After killing a giant worm in the core of the mall, everything changes back to normal. Heather decides to use the subway to get home, but as she walks through the mall, she meets Douglas again. Heather accuses Douglas of being on Claudia's side, but he tells her that he was only hired to find her and that he has no idea what is happening. Heather accepts Douglas's words, and faintly remembers that she forgot something important. She shakes off a strange feeling and tells Douglas she is heading home.
After exploring a subway, an underground passageway, sewers, and a construction site, Heather finds a way into the Hilltop Center. While inspecting a bathtub, Heather suddenly enters the nightmare world once again and falls unconscious. Just before coming to, Heather hears her father's voice in her mind. After the transition, Heather kicks the bathtub in frustration and yells, "Did Claudia do this too!?". In Green Ridge Mental Health Clinic, Heather may find a photo of herself with "Find the Holy One. Kill Her?" on it. Heather soon encounters a man named Vincent Smith, who is also a member of the same cult as Claudia, but has different views on God being birthed. Vincent confirms that Heather has a forgotten past and calls Heather's father a "sneaky guy", causing Heather to yell, "Don't talk about my dad like that!". Before leaving, Heather voices her disbelief about Vincent not being on Claudia's side.
Heather eventually finds a way out of the Hilltop Center and upon entering her apartment, she discovers her father brutally murdered, his lifeless body slumped in a chair. Heather, shocked and speechless at her father being taken away from her so suddenly, rests on her father's lap and sobs heavily. Once she regains control of her emotions, Heather follows a blood trail to the apartment's rooftop, where Claudia is waiting for her. Heather angrily demands an answer from Claudia as to why she killed Harry, and Claudia answers that it is revenge for seventeen years and to fill Heather's heart with hatred. Claudia locks Heather on the apartment rooftop with the monster which took her father's life.
After killing it, Heather returns to her apartment where Douglas is waiting for her. Despite Douglas's apologies, Heather yells at Douglas furiously and blames everything that has happened on him. Once Heather is settled down, Douglas helps her move Harry's body into his room, covering him with a white sheet and lilies. Heather decides to find Claudia and kill her in revenge, even though Douglas doesn't agree. Douglas offers to drive her to Silent Hill since he is also responsible for Heather's loss, and she eventually agrees. Heather sighs heavily and pays her final respects to her father before departing.
Douglas gives Heather a map of Silent Hill and a notebook that her father was holding. Upon reading the notebook, Heather learns that it contains the truth about what happened seventeen years ago. During the car ride to Silent Hill, Heather sits silently in the passenger seat while Douglas tries to make conversation with her. Having read the notebook, Heather tells Douglas about Alessa Gillespie, Dahlia Gillespie's failed attempt at birthing God using her own daughter, and her own birth. Heather then takes a moment to tell her father that she never had a chance to tell him about the happiness that he gave her. In Silent Hill at Jacks Inn, Douglas tells Heather to meet him once she explores Brookhaven Hospital.
While searching the hospital, Heather may find notes addressed to her by Stanley Coleman. On the third floor, Heather is phoned by Leonard Wolf, Claudia's father, resentful of his own daughter and willing to help Heather stop her. However, upon the two meeting, Leonard becomes hostile when he realizes that Heather is not a member of the Order. Heather kills Leonard and takes the Seal of Metatron with her. Upon returning to Jacks Inn, she meets Vincent once more, who tells her to go look for Douglas at the Lakeside Amusement Park.
As she explores the amusement park, Heather re-lives her initial nightmare, only this time she jumps off the tracks in time to avoid the oncoming roller coaster. She then finds Douglas, wounded from a confrontation with Claudia. Having bonded with him, Heather tells him to wait as she goes to locate Claudia. In the amusement park's carousel, Heather is confronted by the Memory of Alessa, who attacks her with various weapons in an attempt to stop the birth of God. Heather beats her and she vanishes, allowing Heather to make her way to the chapel.
Heather encounters Claudia inside the chapel and tells her that Alessa is fine with the way the world is. It is unknown if this was actually Alessa, or just Heather pretending to be her as a way of manipulating Claudia. Claudia has a strong will and explains that there is too much suffering in the world and the God of her cult will change all that, although Heather explains that suffering is a fact of life and that as long as life exists, there will always be some sort of pain and suffering. Heather also explains that you just have to face that reality and try to deal with it as best as you can. Finally, Heather tells Claudia that murdering her father is an unforgivable act. Heather suddenly feels pain in her womb, as the God is close to being ready for birth, and Claudia leaves.
While fighting her way through the corridors of the church, Heather encounters Vincent inside the library. She is irritated by his appearance and questions why he is helping her and Vincent replies that it's because he truly is on Heather's side. He also reveals that he does not feel like stopping God's birth himself, thinking that its birth would not be "convenient" and "unpredictable", although he isn't worried about whether or not Heather is in danger. Heather becomes angered at Vincent for using her and Vincent makes a cruel joke regarding the monsters which for a moment makes Heather think that she was killing human beings. In the end, Heather realizes that she shares the same motive with him. He asks her about the Seal of Metatron, which Heather has in her possession. Vincent is relieved, as he believes it can be used as a weapon to defeat Claudia. He provides her a book called "Otherworld Laws" which contains important information about it, before leaving.
Heather finally catches up to both Claudia and Vincent who are arguing inside the cult's inner sanctum. Vincent urges her to kill Claudia, and Claudia stabs him twice, killing him, telling Heather that the Seal of Metatron will not actually prevent the birth of God. Feeling extremely sick from being pregnant with God, Heather ingests the Aglaophotis inside her pendant, which promptly makes her vomit out the bloody unborn God fetus onto the floor. Heather attempts to crush God under her boot, however, Claudia ingests it and gives birth to it, which brings her demise. Heather is annoyed that she was not able to complete her revenge on Claudia; fortunately for Heather, she is spared from the act of murder.
Heather confronts the partially-formed God, killing Her. After God is killed, Heather kicks the god a few more times to ensure Her defeat, but also likely due to pent-up anger at the whole ordeal. Heather then drops to the floor and mourns her father, trying to cope with the reality that he is still dead. Just as she is ready to leave, Heather looks behind her at something unseen by the player, which may have been Harry's presence or a newborn baby's crying wail, but it is kept a mystery.
In the Normal ending, Heather returns to Douglas at the amusement park, who is alive. Heather shows her rather dark and twisted sense of humor when she plays a really cruel joke on Douglas which made him believe she was going to kill him. Heather comes to terms with her past and ostensibly returns to her normal life. She also switches back to her real name, Cheryl Mason. Cheryl is then seen kneeling while visiting Harry's grave, having given him the decent burial she wanted. Because a memo in Silent Hill: Homecoming states that Douglas Cartland exposed the Order, the Normal ending is canon.
Second playthroughs can result, depending on certain requirements, in either the Possessed ending, where Heather murders Douglas and stares at his body, having been possessed, or a joke UFO Ending, where Harry is still alive and commands aliens to destroy Silent Hill. The joke UFO ending claims Cheryl divorced and is a "young mom who goes it alone" with two children and "it's so hard to raise them and still go to work". It is unknown if this is true and actually canon. If it is, then it calls into question whether or not Cheryl's two children have inherited Alessa's psychic powers, or if Cheryl still retains them. Otherwise, Cheryl's life after Silent Hill 3 has remained a mystery.
Silent Hill: Book of Memories
Heather makes a cameo in the Silent Hill: Book of Memories joke ending, seen running the service desk at the motel. She listens to the guests banter about Silent Hill, much to her annoyance, until one of the managers tells her that one of the guests in Room 302accidentally locked himself in. She then slams her head on the table in frustration, knocking herself out.
Apart from the joke ending, Heather is also a playable DLC character class. She is voiced by Amanda Winn-Lee and many of her quotes are from Silent Hill 3.
Silent Hill: Downpour
Heather makes a cameo in the Surprise ending in Silent Hill: Downpour, in which she surprises Murphy Pendleton with cake. Her vest has sleeves, which is likely a nod to Silent Hill: Revelation.
Silent Hill: Revelation
Heather Mason appears in the film Silent Hill: Revelation, played by Adelaide Clemens. As with her game counterpart, she is an incarnation of Alessa Gillespie, who has been on the run with her adoptive father from the Order since she was a child. She also uses an alias (Heather) instead of her true name and dyes her hair blonde.
Notable differences include Heather initially being only one part of Alessa's soul while Dark Alessa/Memory of Alessa is the dark side, her real name being Sharon Da Silva and a romance with Vincent Cooper, the film's version of Vincent Smith. This is ironic because Heather in Silent Hill 3 comments that she hated Vincent. She is also not pregnant with God, although Claudia still intends to birth God through Heather's body using an impregnation ritual.