Clare Harrison is a supporting protagonist and the first on-screen victim of Billy in the psychological horror film, Black Christmas. She is depicted as somewhat innocent and naive, and is constantly at odds with Barb, one of her sorority sisters and a mouthy drunk. Clare is portrayed by Lynne Griffin.
Clare is introduced as a somewhat prudent and naive girl who is new to Pi Kappa Sig, and is described as having a difficult time fitting in with the other girls, according to Jess Bradford, whom she presumably got along with. Clare was also in a relationship with another student and hockey player named Chris Hayden, who was well-liked in the community. The only person who Clare seemed to have any issue with was Barb Coard, one of her fellow sorority sisters and a mouthy alcoholic. Barb's disdain for Clare was possibly due to jealousy over her relationships with both Chris and her family, while Barb was promiscuous and implied to have a bad relationship with her own mother.
A day before Christmas eve, Clare participated in a Christmas party at her sorority house, along with Chris and the other girls. The party was eventually interrupted by an obscene phone call, prompting Clare and the other girls to listen as Jess answered the call; apparently, they had become the recipients of a mysterious caller, who regularly taunted them with violent sexual comments and curses. Barb eventually took the phone from Jess and mocked the caller, who threatened to murder her, before hanging up. Clare warns Barb not to provoke someone that could be mentally unstable and potentially dangerous, before speculating the same caller could be responsible for the rape of a local girl. After a brief argument with Barb, Clare retreated to her bedroom to prepare for her trip home the next morning.
Clare discovers the housemother's cat, Claude, laying on her bed. After petting the cat, Clare begins packing her things, only to become distracted by what sounds like Claude, hiding in her closet. When she goes over to investigate, the same assailant who had been calling the house jumps out at her, suffocating her with a plastic sheet. The killer proceeds to carry Clare's body to the attic, her face still wrapped in plastic, where he propped her body up in a rocking chair, placing a doll in her lap.
The following morning, Clare's father, Mr. Harrison, arrives in town to pick up his daughter for Christmas break; however, Clare is discovered to be missing and a search soon begins for both her and a local girl named Janis Quaife. Clare's father becomes increasingly unnerved, especially after Janis's disfigured remains are discovered in a local park. Eventually, the police believe they have solved the murder when Jess kills her boyfriend, Peter, in self-defense, though Peter was only emotional over the premature loss of his and Jess's unborn child. In reality, the killer was still lurking in the attic, where Clare and Mrs. MacHenry's corpses remained, undiscovered.