Claire grew up with her older brother Chris after their parents died; with this event, the two developed a very close bond. When Chris joined the U.S. Air Force, she was introduced to his new friend, Barry Burton, and he became a close family friend. After high school, Claire attended university, where she developed her interest in motorcycle customisation, owning two motorcyles herself. Claire also specialized in lockpicking, becoming an expert with skill. After Chris moved to Raccoon City with Burton to serve in Special Tactics and Rescue Service, Claire would occasionally visit her brother to learn hand-to-hand combat and firearms training. He also gave Claire a golden lighter and his S.T.A.R.S. knife.

In August 1998, Chris left for Europe to investigate Umbrella.[10] After weeks of not hearing from her brother, Claire left her college in late September for Raccoon City to find out where he was. She stopped at the Mizoil Gas Station in the outskirts on September 29, unaware of the zombie outbreak that engulfed the city for several days. Claire quickly discovered the zombies when investigating the inside of the convenience store to see Daniel Cortini getting his throat ripped out by one of them. Upon leaving she was saved by Leon S. Kennedy, who had also stopped at the station. After driving towards the city, they were separated by a fiery accident, but they both fought their way to the Raccoon Police Station for shelter. Leon and Claire soon discovered the station had collapsed due to the outbreak of the t-Virus, being that the only unzombified police officers were the injured Lt. Marvin Branagh; Elliot Edward, and Police Chief Brian Irons. It is uncertain if Claire met anyone in the station, but she met Lieutenant Branagh, who saved her after that the zombies chased the college student through the shutter door of the East Hallway. Marvin later gave Claire a combat knife and warned her not to hesitate shooting zombies, regardless of being in uniform or not, before also becoming a Zombie after Claire returns to the Main Hall after leaving the Parking Garage. Claire also found Sherry Birkin, the daughter of William and Annette Birkin. They later crossed paths with a psychopathic Chief Irons, who kidnapped Sherry for her pendant. Irons was later killed by William, who had injected himself with the G-virus and turned into a mutant Annette called "G." Sherry and Claire reunited, but after the elevator drop with G Birkin, Sherry was implanted with the "G" larvae. She was sealed in the waste storage vault for safety by her mother who continued the research on her daughter while trying to find the vaccine. Children of a G-virus carrier are more likely to accept a G-virus embryo, and Sherry would have faced death if she was not cured.