(Operation Raccoon City's backstory)
Claire Redfield was an individual who was caught up in the Raccoon City Destruction Incident
After arriving in Raccoon City, Claire and Leon were separated due to a crash and extraction for the U.S.S. was postponed in order to investigate the crash site. After encountering Leon, the U.S.S. attempts to eliminate him, but he manages to escape.
After discovering Leon's whereabout in the Umbrella lab, Umbrella agreed to locate Leon and intercepted a distress call from him. They learned that Leon was accompanied by Claire Redfield and Sherry Birkin, and that they have taken refuge at the Londsdale Trainyard. Umbrella informs the U.S.S. about the G antibodies inside of Sherry and instructs them to eliminate Claire and Leon in order to capture Sherry.
After a brief battle with Claire and Leon, the U.S.S. are finally able to catch up with Leon and threaten to kill him if Claire doesn't bring Sherry to them. Though reluctant, Claire agrees to bring Sherry to them.
Defend Leon - If the player chooses to save Leon, the U.S.S. decides to let Claire, Sherry, and Leon live due to a disagreement with Umbrella. The U.S.S. decides that Leon isn't the leverage they wanted and they let Sherry stay with Claire and Leon.
Eliminate Leon - If the player chooses to eliminate Leon, the U.S.S. will stick to their original plan of killing Claire and Leon. With Leon already dead, the U.S.S. has to finish the job by killing Claire.
What if: ECHO SIX
After reaching the sewers, the Echo Six team meets Claire Redfield. After exploring the sewers in search of Sherry and being ambushed by William Birkin, Claire separates from them in order to find an exit while they continue their search for Sherry.
After finding Sherry, they meet up with Claire again, but are attacked by William for a second time. As Claire and Sherry escape with the help of another Spec Ops team, the Echo Six team are forced to kill William.
After discovering Sherry has the G-virus, they receive a distress call from Leon and make their way to the Lonsdale Trainyard in order to safely extract the three from the city and stop Umbrella from getting the G-virus.
After successfully rescuing Claire, Sherry, and Leon from Umbrella forces and defeating a mutated T-103, Claire and the others are safely extracted from the city while the Echo Six team stays behind to take care of the threat in Raccoon City. She also appears as a playable character in Heroes Mode.