Stacey Baker was a doctor who volunteered to help the inmates within Arkham City.
Stacey Baker was present in Arkham City when the game took place. She was kidnapped by Harley Quinn when she and her gang attacked the church medical center. She was taken back to the Sionis Steel Mill in an ice cream truck. There, she was forced to inspect the Joker, to try to cure his illness. She was unsuccessful, and was thrown from Joker's office to the factory floor, where she was to be executed by Mister Hammer. However, Joker changed his mind and his henchmen took her to the smelting chamber to be tortured. However, Batman arrived and rescued her. It was Stacey who told Batman of the Joker's TITAN poisoning.
When Batman later returned, Stacey mistook him for a hostile and attempted to attack with a pipe but the Dark Knight parried her attack. After she apologized, she warned Batman that the Joker's men were setting up mines in the next room.