In Scream, 25 year old Dwight "Dewey" Riley is the deputy sheriff of Woodsboro, making it his main duty to protect Sidney Prescott from the killer.
During the film, Dewey develops feelings for Gale Weathers. During the film's climax, he is stabbed in the back by the killer, though he survives.
Dewey was originally supposed to die after being stabbed in the back by Ghostface, but Wes Craven liked the character so much that he decided to film a shot of Dewey being carried into an ambulance in case audiences liked the character also. Sure enough, Dewey was a hit with audiences, primarily due to how cool he thought he was, and Wes Craven decided to use the ending where Dewey lives. If you look closely, you can see that whenever Dewey is lying unconsious, he isn't breathing, because he was supposed to be lying dead.
He arrived once again to protect Sidney. Only this time, he has a limp due to a severed nerve caused by his injury in the previous film. Angry at Gale Weathers, who had depicted him as inexperienced in her new book about the murders, Dewey constantly tries to avoid Gale's presence and is rude to her whenever he can't. Later on, Gale and Dewey have a brief emotional moment, only to realize that Ghostface is in fact in the same building. After being separated, Dewey is stabbed several times, with Gale a witness in a soundproof room, directly on the opposite side of a window showing Dewey's location. However, once again, Dewey survives the ordeal.
Dewey is still a police officer in this one, seemingly on leave to act as a "technical advisor" on the set of the film Stab 3. After a new killer has surfaced, Dewey aids in the investigation.
By this point things are still a little bit tense towards Gale and Dewey, and it appears that there are feelings between him and the actress portraying Gale, Jennifer Jolie. By the end of the film, however, things are patched up yet again between Dewey and Gale.
He and Gale arrive at John Milton's mansion following a phone call that they thought was from Sidney; however, it was actually from the killer, using a voice changer to sound like Sidney. Later, they burst in after Sidney has defeated (and stabbed) Ghostface, who was director Roman Bridger. After Roman jumped to his feet, Dewey shot him in the chest several times, but it wasn't effective due to Roman wearing a bulletproof vest. Sidney shouted for Dewey to shoot Roman in the head, and Dewey did, killing Roman.
Afterward, Dewey proposed to Gale, and she accepted.
Dewey is now the Sheriff of Woodsboro and married to Gale Weathers, who is adjusting to small-town life with great difficulty. Alongside his deputy, Judy Hicks, and the rest of the Woodsboro police force, Dewey is in charge of investigating the newest slew of murders. He drives Gale to the hospital after she is stabbed in the shoulder, and later receives a phone call from Judy while he is in the car afterward. Judy informs him that the poilicemen he told to protect the Roberts house are both dead, along with Kate Roberts, Sidney's aunt. Dewey stops the car and drives there. He, Judy, and the rest of the police arrive to find Sidney and her cousin Jill Roberts unconcious on the ground, near the corpses of Trevor Sheldon and Charlie Walker. They assume that Trevor and Charlie were the killers and take Sidney and Jill to the hospital. Dewey visits Jill and they talk, with Dewey revealing to Jill that Sidney survived, but might not remember anything when she wakes up. Jill states that she and Gale should write a book together, as both of them were stabbed in the shoulder. Dewey then visits Gale, who asks him how Jill knew where Gale was stabbed. Dewey realizes that Jill is the killer and calls Judy over to help him and Gale save Sidney from Jill. As soon as Dewey arrives however, Jill knocks him out by bashing his head with a bedpan six times. Dewey survives, and Gale runs off to get doctors for him after Jill has been killed (by Sidney). By the time Scream 4 rolls around, Dewey is more confidant and serious. He has also mostly recovered from his limp through physical therapy.