Secretly the illegitimate son of an American soldier and an Australian woman, Harkness was raised in poverty, during which time he developed great skill in making boomerangs, and in using them as weapons. As a young adult, he was hired as a performer and boomerang promoter by a toy company which was, unbeknownst to him, owned by his biological father. Audiences ridiculed him, and a resentful Harkness turned to using his boomerangs for crime. Although he lacked any actual superhuman abilities, he became a recurring enemy of The Flash, typically by devising altered boomerangs which could produce astonishing effects, and using them ruthlessly. He became a staple member of The Rogues, a group of villains dedicated to opposing Flash.