Douglas's original motive is to return Heather to Claudia. Douglas talks to Heather Mason after she finishes her phone conversation with her father at the Central Square Shopping Center. Douglas requests for some of Heather's time to which she clearly states her disinterest. Douglas states that it's about Heather's birth, which still isn't good enough to interest her. He follows Heather, but can only go so far, as she enters the bathroom.
Douglas, waiting in the shopping mall's lobby, finds Heather after she kills the Split Worm. He reveals that he has also encountered a monster, but Heather interrupts him. She accuses Douglas of being in on it with Claudia, but realizes that Douglas is just as shocked as she is. Heather decides to head home using the subway.
In the Daisy Villa Apartments, Douglas discovers Harry Mason's corpse. Douglas calms Heather down and they lay him in bed. Despite not agreeing with Heather's revenge plan, Douglas states that he feels responsible and offers to take Heather to Silent Hill to murder Claudia in retaliation for Harry's death. When Heather tells Douglas he might die, he replies, "That's fine. Nobody's gonna cry over my grave anyway." He then heads out to get his car ready.
Outside the apartment building, Douglas greets Heather, and reveals that Vincent Smith gave him a map and told him to go look for Leonard Wolf upon arriving in Silent Hill. Douglas gives Heather the map and Harry's notebook and they drive to Silent Hill.
During the car ride, Douglas and Heather discuss the rumors of Silent Hill, and Heather's past as Alessa Gillespie. Heather also recaps the events of the first Silent Hill. Douglas mentions he went to Silent Hill once on a missing person's case, which may possibly be a reference to James Sunderland from Silent Hill 2. Douglas sits silently in the car, listening to Heather's feelings about her father's death.
When they arrive in Silent Hill, Douglas and Heather stop at Jacks Inn. They briefly discuss being afraid to be alone; Douglas admits to being afraid, and then heads for Leonard Wolf's house. Eventually, Douglas returns to the Inn before Heather comes back from Brookhaven Hospital. Douglas leaves a message for Vincent to tell Heather to head to the Lakeside Amusement Park, where Claudia apparently is.
At the amusement park, Douglas speaks with Claudia and becomes angry that she deceived him. Claudia once again explains her whole plot, and Douglas, like everyone else, disagrees and mocks her. Douglas then raises his gun to Claudia, who challenges his readiness to kill her. Whatever happens after the cutscene leaves Douglas badly injured, to the point he feels his leg is broken. It may be possible that supernatural powers possessed by Claudia came into play here because there are no monsters present in the cutscene.
When Heather arrives at the amusement park, she discovers that Douglas's leg is broken. Douglas tells Heather she reminds him of his late son. He also tells Heather, as she leaves to confront Claudia, that perhaps if he killed her instead, his nightmare would end. Heather, nervous, doesn't feel offended, and takes a deep sigh before she continues on her way.
In the "Normal" ending, after Heather kills the God, she pretends to be possessed and startles Douglas before nearly stabbing him. Douglas says Heather has bad taste in jokes, but Heather interrupts, telling Douglas to call her Cheryl. In the "Possessed" ending, Douglas is killed by Heather. This ending can only be unlocked after completing the game once.
and in silent hill homecoming it was revealed in a memo that he was the one who exposed the order to the public sometime after the events of silent hill 3.