Dr. William Birkin was assigned to work on the G-Virus project. During September 1998 he was infected with the G-Virus and mutated, the reason of the infection is unknown In the story, he is encountered by Elza Walker in the factory where he makes his appearance by calling for his daughter, "Sherry" and he is also fought by Leon S. Kennedy in the Underground Labs. He attacks the duo numerous times in the lab and is confronted for the last time in the Umbrella Train, Annette birkin aids the protagonists to stop him.