No one in the Batman Family had an easy childhood, but Cassandra Cain may have had the worst. Raised from infancy under the tyrannical thumb of her father, the world-class assassin David Cain, Cassandra was taught violence before she was taught anything else—even how to speak. Yet, despite her father's abuse, Cassandra understood the difference between good and evil. As she grew older, she realized what her father had done to her and escaped him, fleeing to Gotham City where her life would be forever changed for the better.
Duke Thomas is the daytime protector of Gotham City, and his metahuman light sensory powers make him unlike any of Batman's other crimefighting partners.
While Batman and most of his allies operate at night, crime in Gotham City is quite different in the daytime, and so requires a different kind of crimefighter. Enter Duke Thomas—a.k.a. the Signal, the brightly colored agent of the Bat who hits the streets when the sun is out and Batman is asleep in his cave.