Dr. Kellerman was one of the doctors who was kidnapped by the Joker's Henchmen. He, along with Aaron Cash, were trapped in the Patient Observation Room, which was full of laughing toxin, until Batman appeared and rescued them. When meeting with the other rescued doctors and Batman in the Sanatorium, Dr. Young insisted on going to the Arkham Mansion to retrieve her notes. Cash agreed to escort her to the Mansion and, after that, to a safe hiding place. They left. Batman noticed more henchmen coming up the elevator. He advised the remaining doctors (Dr. Cassidy and Kellerman), to go back to the Patient Observation Room and hide there. They remained there for the rest of the game, and survived the incident along with Dr.Cassidy and an unnamed doctor. The doctors in the Patient Observation Room survived Joker's takeover. It was assumed that he returned to his usual duties at the asylum until it was closed down by Mayor Sharp.