Heather Mason is the adopted daughter of former Silent Hill protagonist Harry Mason, who was the lead in the original game. After defeating the final boss, The Incubator, the canon ending of Silent Hill leaves Harry outside the border of the cursed town with a small child that turns out to be the reincarnated form of both Cheryl Mason and Alessa Gillespie.
Before Silent Hill 3
Prior to the events of Silent Hill 3, Harry Mason tries several attempts to distance himself and his daughter away from Silent Hill and the dangerous cult that resides in it. The first of which is renaming his daughter Heather and dying her hair blonde and moving to a distant, currently unknown, location. Unfortunately the cult did not give up so easily and eventually chased the family down. Heather and her father were forced to flee once more, eventually ending up in the Daisy Villa Apartments in a town close to Silent Hill.
The Events of Silent Hill 3
Running an errand for her father at the Central Square Shopping Center, Heather Mason is visited by several visions of the town of Silent Hill, most likely memories implanted by Cheryl and Alessa from when they were still alive. She quickly finishes up her time at the mall but not before being confronted by Douglas Cartland, a private investigator, who approaches her. Before he can say much Heather runs away thinking that Douglas must be another stalker with some relationship to the cult members she and her father frequently came across. As she explores the rest of the mall the world around her quickly transforms into a hellish environment filled with grotesque monsters.
She eventually comes across a slender, white haired woman who calls herself Claudia. The woman preaches about the coming of the new God and how the world around them is slowly moving towards the forgotten paradise. The two quickly part ways as a migrain overwhelms her. These will plague Heather for the rest of the game whenever she travels to and from the Otherworld or whenever her mysterious past is brought up. She continues to travel across the town, finding her way back to her home, coming across even weirder and even more disturbing creatures along the way. The whole time Heather hoping that this is all indeed just a dream. She eventually finds an odd man, names Vincent, who claims to be working alongside Claudia. The two have different goals in mind however, but the man comes off docile enough for Heather to not feel as threatened by him compared to his female counterpart.
Unfortunately she soon comes to the realization that it is indeed very real, at least for her. Heather eventually reaches her home hoping to find her dad their to greet her, only to find his bloodied corpse laying limp on his recliner. Overcome with grief and anger, she follows a blood trail leading to the roof of the apartment complex where Claudia and a beast known only as the Missionary wait for her. A fight ensues, leaving Heather victorious and the Missionary dead while Claudia escapes to parts unknown. Douglas Cartland appears once again and offers to take Heather to Silent Hill, where the religious cult that Vincent and Claudia are affiliated with is situated. The disire for revenge fills her heart and Heather accepts the offer.
The two arrive in Silent Hill and are quickly separated as Heather visits the town hospital in search of answers. Parts of her past begin to flow through her mind as she travels once again into the Otherworld. Knowledge of Claudia's past and relationship to her and the town begin to become clearer. The first incarnation of Alessa and Claudia were originally quite close to one another, but Claudia was always overshadowed by the legend of the young girl. Heaher realizes that she and the town are indeed connected in the past through several instances of Otherworld beings leaving notes for her in rooms, calling her on payphones, and confronting her in the flooded basement of the building.
Heather eventually confronts her past self before the final confrontation with Claudia and the religious cult. The battle leaves her with a stronger emotional and mental sense of worth, but at the same time only fueling her hatred for Claudia who she feels must be stopped in order to rectify the death of her father and save the world from being destroyed by the cult's God being reborn. When she finally finds Douglas again, he has broken his leg due to a previous encounter with Claudia, but he continues to try and reason with Heather but with limited success.
The final confrontation with the religious cult sends Heather into a form of "labor" when Claudia begins the incantations for the resurrection of the God of Paradise. Heather acting quickly swallows a jewel Harry had given her long ago which was designed to expell evil beings. Heather Pukes out the God, leaving a lifeless sack on the ground. Claudia jumps at the opportunity to save her God and at the same time giving her life the meaning she wished it had had all along by swallowing the creature whole and giving birth to it herself, killing her in the process.
After Vanquishing the God, Heather leaves the town's church and finds Douglas still alive. The two leave Silent Hill together, before leaving though, Heather claims that she is no longer running away from her past and would like to be called Cheryl from then on.