A lonely and insecure 12-year-old, Sherry is quite mature for her age. She is very shy and when she speaks, she lacks self-confidence and always has the feeling she is lost. Sherry's parents are too wrapped up in their work to heed the emotional needs of their child. My parents are Annette and William Birkin.
Sherry was born in 1986 to Umbrella Corporation top scientist William Birkin, and his assistant and wife Annette Birkin. Due to their key participation of developing biological weapons for Umbrella, William and Annette's work schedules were very intense and busy, and as such weren't around as Sherry grew up. Nevertheless, she loved her parents very much and enjoyed spending whatever time she had with them, with her parents feeling the same way. In 1995, William and Annette were transferred from the Arklay Research Facility to a newly-constructed underground laboratory in Raccoon City to finish William's work on a new biological weapon called the G-virus. It was finally finished in 1998 though William refused to hand the virus over to Umbrella (despite his offered place on it's executive board), instead preferring to hand the virus over to the U.S. Government in exchange for a larger reward. As such, an Umbrella Special Forces Unit was sent in to forcefully retrieve the G-virus, which was done after fatally injuring William in a hailstorm of bullets. Knowing he was about to die, William injected himself with the G-virus, turning into a hideous monstrosity, hunting down and killing all but one of his assailants. As he did so, several vials containing the t-virus, kept in a sample case stolen by the Umbrella soldiers, were scattered on the ground and broke; and rats interacting and consuming the liquids carried the infection to the rest of the city.
Sherry remained unaware of this, especially the fact that Raccoon City was nearly totally consumed with zombies. Annette contacted her daughter, and implored her to seek refuge in the Raccoon City Police Department, though by this time it too had been overrun and most of it's personnel were now undead. Sherry did so, unaware of this latest development, and remained in hiding, seeking sanctuary from the zombies, Umbrella's escaped B.O.W.'s, and later her mutated father and the Tyrant T-103 known as T1 (who had come for a G-virus sample secretly entrusted to Sherry by her mother in her locket). Soon, Sherry encountered another survivor; Claire Redfield (while searching for her missing brother Chris Redfield). With Sherry gaining Claire's protection and friendship, the two worked together to escape the infested precinct house, and later the city.
Soon, they were increasingly cornered by T1 and "G" (William), and were eventually driven into Umbrella's secret underground lab. Sherry and Claire were separated, and soon Sherry was soon cornered by T1. Just in time, Claire got Sherry to throw her the locket, having by this time been told what it contained by Annette. Claire threw the locket into a melting pool, with T1 mindlessly following it to his death. Suddenly, the facility's self-destruct activated, and several minor explosions caused debris to fall and fatally injure Annette. Sherry came to her mother's side in her final moments, and Annette was able to apologize to Sherry for not being a better mother and expressed her love for her daughter before dying.
Sherry and Claire soon found the lab's emergency escape train, and, upon rejoining fellow survivor and rookie police officer Leon S. Kennedy, the train headed for the city limits. "G" made one last attempt to kill the three survivors, but failed, as, while Leon and Claire distracted "G", Sherry managed to locate and pull the train's emergency brake, allowing them to escape the train and get far enough away before the train, it's anti-biohazard self-destruct mechanism activated by "G"'s presence, exploded, taking "G" with it.
Upon their escape, Leon, Claire and Sherry were rescued by U.S. official authorities, and, while the former two went off to continue the fight against Umbrella, Sherry was given into government custody. Sherry was initially reluctant, but Claire assured her they would meet again, leaving her prized pink vest with her as a reminder of their time together.