in the end of silent hill 1, the incubator gives harry mason an infant child to take with him away from silent hill, this child ends up becoming the protagonist of silent hill three (silent hill two is unrelated to the plotline of 1 and 3) known to the player as heather mason. originally, heather was named cheryl, although harry had thought this was a mistake and that at the time of naming her he was thinking of his previous child cheryl that ended up being alessas second half.

heather mason is a reincarnation of alessa and cheryl, she is the same but also different from her, because of this she is still a target of the order, the religious doomsday(?) cult from the first installment of the franchise as, like alessa, heather is pregnant with the fetus of god however she is unaware. harry likely has no idea she still has god inside her, however regardless if he had an inkling or not, on one of her birthdays he gives her a pendant with crystallized aglaophotis. aglaophotis can be used to expel demons to keep one safe. (this will be important wayyyyyyyy down the line)

17 years after her birth, heather finds herself waking up from a nightmare that takes place in the lakeside amusement park of silent hill where she presumably dies in a roller coaster accident. upon waking up, she leave the fast food join she was in and goes to call her dad in the mall and let him know shes on her way home. after calling, she gets bothered by a man named douglas, a private investigator, who unintentionally started the events of the entire game by asking heather to come with him as someone wants to meet and talk to her. (from heathers perspective at least, really its claudia/the orders fault)

heather manages to leave his line of sight and navigate the nightmarish hellscape that is the otherworld mall among other areas and finally returns home, only to see that someone had murdered her father. she follows a blood trail up to the roof where she meets claudia again.

claudia is a member of the order who was sent to look for heather/alessa in hopes of bringing her back to the church to usher in paradise with the birth of god.

when she meets with claudia, heather threatens to kill her. claudia denies her doing that as she isnt the one who killed heathers father, points to the entity that did kill him, and says to follow her to silent hill. upon finishing her business on the roof of her apartment buildings, she sees douglas in her apartment where after an argument, they give an impromptu funeral service of her father and talk about what heather is going to do now.

heather says she is going to go to silent hill so she can get revenge and kill claudia, while douglas disagrees with this course of action because he doesnt think itll do any good, he agrees to drive her there and help her look for claudia. before she gets in his car, she grabs some stun gun batteries and her stun gun to take with her to silent hill for self defense. (i havent mentioned it yet but silent hill games are survival horror lolz)

upon coming out of the building, douglas says he ran into a guy named vincent who said to look for a guy named leonard. vincent is another member of the order, however he seems to be motivated in ways different to claudia, despite still being a whackass weirdo.

upon arriving to silent hill and sleeping in the inn, douglas and heather part ways to search around. heather goes to the brookhaven hospital where she navigates through the normal world and otherworld hospital to meet leonard, only to end up killing him.

upon killing him, he leaves the symbol of metatron, which later described in the churches library, is a symbol that basically does the order harm. (lol)

after leaving, she returns to the inn they stayed at, only to not find douglas but vincent again. he tells her that douglas is still out and that he is at the church across toluca lake, and the fastest way to the church is through the amusement park from her dream. (1/2)