Bright, outgoing, well-liked, Kelly Brand was an active member of her school, athletic but with something of a geeky side. She always knew her mother was famous, but thought it was simply that Kim Brand was a retired movie star. She had no idea that her mother had been the heroic Fly-Girl, not only fighting crime but serving as a sentinel to guard Earth from alien invasion. Estranged from her father (Paul Patton Jr. aka the Fox), Kelly was raised by her mother, who instilled in her a sense of responsibility and loyalty.
When the Brain Emperor attacked a reunion of the original Mighty Crusaders, Kelly's mother was apparently killed, but she was saved by her mother's old teammate The Shield, as were the five other teenagers that had been at the party. From this old hero Kelly learned the truth about her mother, and learned that she had wanted Kelly to follow in her in her footsteps should the worst occur. Taken in by The Shield, Kelly was teleported deep into space to meet with her mother's old friend and fellow hero, Bob Phantom. Bob, now the sole guardian of a transdimensional listening station used to detect potential threats to Earth, first filled Kelly in on the ancient intergalactic wars her mother had become entangled in, and then gave the teenager two pieces of gear built to replicate the science-bordering-on-magic that had once fueled her mother's superpowers: a harness which boosted Kelly's physical stats and gave her wings enabling flight, and a pistol capable of firing concentrated, paralyzing beams (or lethal blasts if needed) Kelly found herself thrust into the role of Earth's Last Line of Defense against any alien invaders, especially the Erichni, a powerful inter-dimensional race of conquerors. She accepted her new role, finding some solace in the fact that it - in a way - helped her feel closer to her mother, and joined the New Crusaders as the new Fly Girl.