Dr. Isaac was a medical doctor employed by Raccoon General Hospital.
He was present at Main Street, alongside dozens of police officers, nurses and fellow doctors, following the successful completion of "Operation: Mop-Up", as the survivors attempted to regain control of Raccoon City.
Like almost all hospital staff, he was infected by the t-Virus while the hospital was dealing with zombified patients. He transformed into a Zombie and attacked the survivors as they searched the hospital for supplies.
He is unlocked by beating The Hive scenario on Normal difficulty and costs 6,000 points. He has a Hemostat in his inventory. He can be unlocked in File #2 and purchased for a cheaper price by using the Data Convert option. He is a George-type character.
There is a second version of him used for Zombies that can only be used with cheating devices. This version lacks proper stats, resulting in being unable to damage enemies and running very slow. The only way to fix this is to use stat modifier cheating device codes.