Katherine "Kate" Kane and her twin sister, Elizabeth "Beth" Kane, were born into the wealthy Kane family in Gotham city. On their twelfth birthday, Kate and Beth were taken out to a restaurant by their mother where they were kidnapped and held for ransom. Their father, Jake Kane; a military colonel, launched a rescue attempt but only Kate survived the conflict; her mother and sister killed by the kidnappers.
Years later Kate attended the United States Military Academy only to be expelled, despite her excellent grades, due to her sexual orientation. Returning to Gotham she began to suffer depression over having no life direction, however a chance mugging-attempt resulted in her meeting Batman saw her inspired and she attempts to fight crime using her father's military equipment in secret.
Discovered by and further assisted by her father, Kate is sent on a two year training regime after which she returns to Gotham to find a Batsuit and secret bunker ready for her use.