Kathy pretends to be a girl with too much time and money on her hands. She does not have a good relationship with her father, though he orders she be protected by his hired bodyguards at all times. Kathy becomes attracted to Bruce Wayne, aka Batman.
Kathy blames her father for the death of her mother, who died when an attempt on Carlton Duquesne's life was made. Carlton's wife was killed instead. Kathy's mother was supposedly a gifted artist, a skill Kathy inherited from her. Kathy took this skill, enrolling in art classes, where she met Sonia Alcana. Along with Alcana and Dr. Roxanne Ballantine, Kathy devised a scheme to enact revenge on her father, Rupert Thorne and the Penguin, the latter two receiving grudges from Alcana and Dr. Ballantine. The three would take turns becoming Batwoman, taking down Thorne, Penguin and Duquesne's weapon smuggling racket one step at a time.
Kathy was Batwoman the night of the final operation of Thorne and Penguin's smuggling racket. Her mission was to place a charge aboard their luxury cruise liner, taking the weapons and, more importantly, everyone on board with them. What Kathy did not anticipate was Bane, who captured Batwoman. The Penguin realized that Kathy Duquesne was at his club, The Iceberg Lounge, the night that Batwoman attacked the club. He finally realized the entire scheme. Kathy and her father were reunited as he saved her from the now burnt-to-a-crisp cruise liner.
Kathy's name is similar sounding to the original Batwoman's, Kathy Kane, as it's pronounced "Du-kane". According to story writer Alan Burnett this is due to the fact that DC Comics requested they not use "Kathy Kane" as the film's Batwoman has a slight villainous side. Burnett admitted he liked the idea as it would help keep people from guessing the solution of the mystery by adding a red herring clue.