Little is known of Annette's early life other than her training as a virologist which earned her a career at Umbrella U.S.A.'s Arklay Laboratory, under the head of research, Dr. William Birkin. The two married in the mid-1980s and by 1986 Annette had given birth to their daughter, Sherry. While they remained married, Annette felt they had prioritised their research careers over it.
Following her husband's 1988 discovery of the Golgotha Virus, Umbrella HQ began heavily funding the resulting project, with the construction of a massive laboratory complex located in the Arklay Mountains deep below the Umbrella Chemical Plant being completed in 1991. Publicly, the Birkins were treated as its managers, but this was only part of the facade to disguise the research. The two spent the next seven years aggressively committed to their new research project, and their daughter Sherry became neglected as a result.
In 1998, the relationship between the Birkins and Umbrella HQ began to quickly wane, with William's hopes of a promotion to the corporation's head office being unfulfilled. Like his friend Dr. Albert Wesker, he felt the need to leave Umbrella, but could not go without the virus being completed. Annette stayed with her husband, as they made preparations to sell the virus to the US military in exchange for protection. With Umbrella having spies within the US military, the gamble was quickly uncovered. Further research funding was cut, and the company made demands for the virus to be handed over.
During these developments, Annette agreed to an interview with freelance reporter Ben Bertolucci, who told her he was doing a story on Umbrella's new scholarship program. Bertolucci instead interrogated her about NEST and Golgotha, alarming her with his information-gathering skills and forcing her to leave. Unknown to her, Bertolucci was in fact working with Ada Wong, a spy for a rival company Wesker had joined.
On the night of 22 September, operators of the Umbrella Security Service infiltrated NEST intent on arresting the Birkins and retrieving the virus. While successful in stealing most of the strains, William was shot in the heat-of-the-moment and left to die. Annette arrived quickly to investigate the disturbance, and found him dying with gunshot wounds. Soon after, he infected himself with Golgotha, which mutated his body to recover his injuries, transforming him into a large and powerful G mutant. Finding him mutating, her love for him prevented her from killing him there and then, against her better judgement. William left the lab, continuing to mutate while chasing the USS team. The subsequent battle resulted in several "t" samples being released into the sewers, allowing rats to be infected, which would later contaminate the city's drinking water. By 24 September, thousands had drank the water, and mutated into Zombies.
Annette meanwhile remained at NEST and Umbrella's sewer facility under Raccoon City. Accounts differ as to if she alerted Sherry to the outbreak and told her to hide at the Raccoon Police Station, or if she did nothing, expecting her to stay home. Regardless of what actually happened, Annette ignored the escalating deterioration of law and order above and focused on researching the increasing population of "G", the mutant children of William birthed asexually. It was not until the early hours of Wednesday 30 September that Annette is known to have met any uninfected survivors. These were Sherry herself, a teenager named Claire Redfield who was looking after her, police officer Leon S. Kennedy, and the spy, Wong. In her encounter with the latter pair, she attempted to kill Wong, already suspecting her of being a spy, but Kennedy took the bullet for her. A second attempt was made on Wong's life, with accounts differing as to if this was another attempted shooting or incineration in a waste processing room, but whichever the case the attempt was unsuccessful.
Whether or not she met Sherry in the sewers is also contradictory, but she did become aware that Sherry was infected with Golgotha by way of parasitism of a G-embryo. She gave instructions to Redfield to obtain a sample of the vaccine within NEST. While as a mother she was frightened for Sherry's safety, as a scientist she had already determined that Sherry's successful mutation into another creature like her father would be a risk to millions beyond the confines of Raccoon City.
There are a number of contrasting accounts as to what happened to Annette in NEST. In one account, she was cut open by William and bled out on the floor. In another, she suffered internal hemorrhaging by falling debris. In another two, she suffered this injury due to an attack by William. Who she died with is also contrasting, with two saying she succumbed to her wounds after another attempt on Wong's life and another saying she died while vaccinating Sherry.[note 1]
↑Due to the contradictory nature of the final sections of Resident Evil 2, it is indeterminate which scenario is canon and, in fact, it may be a mixture of events. The Wiki will deliberately keep this section short and vague unless Capcom confirms the story.