Rebecca, a medic on the S.T.A.R.S. Bravo Team is the youngest of all S.T.A.R.S members (18 years of age). Her training in medicine makes her a valuable asset to the team, but her lack of size and strength can sometimes be a downfall, especially when cornered by several zombies. However, Rebecca proves she has what it takes to be a survivor in the world of Survival Horror.
Not much is known about Billy, except that he is a former second lieutenant for the marines who receives capital punishment for the mass murder of 23 people. The paddy wagon that is transporting him to the prison is attacked. Chaos ensues and taking advantage of the unguarded moment, Billy escapes to the train. This is where he meets up with Rebecca and the two team up to try and survive the nightmare together.
Wesker, commander of Alpha Team and one of the lead researchers on the T-virus alongside William Birkin makes his third appearance in a Resident Evil game. In Resident Evil Zero some light should be shed on the details of how he lured the S.T.A.R.S. members into his "experiment".
One of the lead researchers of the T-Virus for the Umbrella Corporation and also the sole creator of the G-virus, William Birkin makes his second (and most likely last) appearance in a Resident Evil installment. He will do anything to protect his work, including murder.
