Sandra is part of the prestigious Knight family of Opal City. She had given Dr. Abraham Davis, a scientist who had escaped the Nazi's in Europe, asylum and a lab so that he could finish work on his invention, the black light ray. With the black light ray Sandra became the Phantom Lady. She became an agent of Argent a government agency created after the cold war. She was also responsible for her cousin Ted Knight becoming Starman. During her time with Argent Sandra had married her fellow crime fighter Iron Munro. During one of their missions Baron Blitzkrieg, kidnapped Sandra and stolen the fetus from her womb.

After losing her baby Sandra decided to quit spy work and, with the help of her old collegue Roy lincoln, created the University of Our Lady of the Shadows, which was used to train woman spies and to help her track down her missing child. With having no success in finding her child she became the headmistress of the university. She had trained Dee Tyler at the academy and gave her the black light ray to become her the second Phantom Lady.

In the Manhunter series it was revealed that Sandra and Iron had had another child before they got married and given it up for adoption. The child was Walter Pratt, Kate Spencer's father.