The youngest son of Ted Knight, Jack was a classic problem child after the death of his mother. More an artist and dreamer than his father and brother, Jack felt alienated and fell in with the wrong crowd as a teenager, alternatively joining a gang and becoming part of the neo-Punk movement of the early-80's.
Still, Jack did eventually clean himself up, though he still cared little for his father's carrear as a hero. He certainly never planned to take up the mantle for himself. Then The Mist began his crimewave, and Jack's brother David was killed and his father hospitalized. Forced into the role of a hero through familial duty and a desire to keep his city safe, Jack defeated the Mist and his family and has protected Opal City since that day.
Though he would much rather live a quite life running his shop, Jack is always quick to answer the call to action when needed- a fact that has earned him the respect of the police department, particuarly the O'Dare family.
When not fighting crime, Jack spends his time running his store, painting, spending time with his girlfriend Sadie and trying to decide what his next tattoo should be.